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   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/stat.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/smp_lock.h>
  32 #include <linux/swap.h>
  33 #include <linux/string.h>
  34 #include <linux/init.h>
  35 #include <linux/pagemap.h>
  36 #include <linux/highmem.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/key.h>
  39 #include <linux/personality.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/utsname.h>
  42 #include <linux/pid_namespace.h>
  43 #include <linux/module.h>
  44 #include <linux/namei.h>
  45 #include <linux/proc_fs.h>
  46 #include <linux/mount.h>
  47 #include <linux/security.h>
  48 #include <linux/ima.h>
  49 #include <linux/syscalls.h>
  50 #include <linux/tsacct_kern.h>
  51 #include <linux/cn_proc.h>
  52 #include <linux/audit.h>
  53 #include <linux/tracehook.h>
  54 #include <linux/kmod.h>
  55 #include <linux/fsnotify.h>
  56 #include <linux/fs_struct.h>
  57
  58 #include <asm/uaccess.h>
  59 #include <asm/mmu_context.h>
  60 #include <asm/tlb.h>
  61 #include "internal.h"
  62
  63 int core_uses_pid;
  64 char core_pattern[CORENAME_MAX_SIZE] = "core";
  65 int suid_dumpable = 0;
  66
  67 /* The maximal length of core_pattern is also specified in sysctl.c */
  68
  69 static LIST_HEAD(formats);
  70 static DEFINE_RWLOCK(binfmt_lock);
  71
  72 int register_binfmt(struct linux_binfmt * fmt)
  73 {
  74         if (!fmt)
  75                 return -EINVAL;
  76         write_lock(&binfmt_lock);
  77         list_add(&fmt->lh, &formats);
  78         write_unlock(&binfmt_lock);
  79         return 0;
  80 }
  81
  82 EXPORT_SYMBOL(register_binfmt);
  83
  84 void unregister_binfmt(struct linux_binfmt * fmt)
  85 {
  86         write_lock(&binfmt_lock);
  87         list_del(&fmt->lh);
  88         write_unlock(&binfmt_lock);
  89 }
  90
  91 EXPORT_SYMBOL(unregister_binfmt);
  92
  93 static inline void put_binfmt(struct linux_binfmt * fmt)
  94 {
  95         module_put(fmt->module);
  96 }
  97
  98 /*
  99  * Note that a shared library must be both readable and executable due to
 100  * security reasons.
 101  *
 102  * Also note that we take the address to load from from the file itself.
 103  */
 104 SYSCALL_DEFINE1(uselib, const char __user *, library)
 105 {
 106         struct file *file;
 107         struct nameidata nd;
 108         char *tmp = getname(library);
 109         int error = PTR_ERR(tmp);
 110
 111         if (!IS_ERR(tmp)) {
 112                 error = path_lookup_open(AT_FDCWD, tmp,
 113                                          LOOKUP_FOLLOW, &nd,
 114                                          FMODE_READ|FMODE_EXEC);
 115                 putname(tmp);
 116         }
 117         if (error)
 118                 goto out;
 119
 120         error = -EINVAL;
 121         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 122                 goto exit;
 123
 124         error = -EACCES;
 125         if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 126                 goto exit;
 127
 128         error = inode_permission(nd.path.dentry->d_inode,
 129                                  MAY_READ | MAY_EXEC | MAY_OPEN);
 130         if (error)
 131                 goto exit;
 132         error = ima_path_check(&nd.path, MAY_READ | MAY_EXEC | MAY_OPEN);
 133         if (error)
 134                 goto exit;
 135
 136         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 137         error = PTR_ERR(file);
 138         if (IS_ERR(file))
 139                 goto out;
 140
 141         fsnotify_open(file->f_path.dentry);
 142
 143         error = -ENOEXEC;
 144         if(file->f_op) {
 145                 struct linux_binfmt * fmt;
 146
 147                 read_lock(&binfmt_lock);
 148                 list_for_each_entry(fmt, &formats, lh) {
 149                         if (!fmt->load_shlib)
 150                                 continue;
 151                         if (!try_module_get(fmt->module))
 152                                 continue;
 153                         read_unlock(&binfmt_lock);
 154                         error = fmt->load_shlib(file);
 155                         read_lock(&binfmt_lock);
 156                         put_binfmt(fmt);
 157                         if (error != -ENOEXEC)
 158                                 break;
 159                 }
 160                 read_unlock(&binfmt_lock);
 161         }
 162         fput(file);
 163 out:
 164         return error;
 165 exit:
 166         release_open_intent(&nd);
 167         path_put(&nd.path);
 168         goto out;
 169 }
 170
 171 #ifdef CONFIG_MMU
 172
 173 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 174                 int write)
 175 {
 176         struct page *page;
 177         int ret;
 178
 179 #ifdef CONFIG_STACK_GROWSUP
 180         if (write) {
 181                 ret = expand_stack_downwards(bprm->vma, pos);
 182                 if (ret < 0)
 183                         return NULL;
 184         }
 185 #endif
 186         ret = get_user_pages(current, bprm->mm, pos,
 187                         1, write, 1, &page, NULL);
 188         if (ret <= 0)
 189                 return NULL;
 190
 191         if (write) {
 192                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 193                 struct rlimit *rlim;
 194
 195                 /*
 196                  * We've historically supported up to 32 pages (ARG_MAX)
 197                  * of argument strings even with small stacks
 198                  */
 199                 if (size <= ARG_MAX)
 200                         return page;
 201
 202                 /*
 203                  * Limit to 1/4-th the stack size for the argv+env strings.
 204                  * This ensures that:
 205                  *  - the remaining binfmt code will not run out of stack space,
 206                  *  - the program will have a reasonable amount of stack left
 207                  *    to work from.
 208                  */
 209                 rlim = current->signal->rlim;
 210                 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
 211                         put_page(page);
 212                         return NULL;
 213                 }
 214         }
 215
 216         return page;
 217 }
 218
 219 static void put_arg_page(struct page *page)
 220 {
 221         put_page(page);
 222 }
 223
 224 static void free_arg_page(struct linux_binprm *bprm, int i)
 225 {
 226 }
 227
 228 static void free_arg_pages(struct linux_binprm *bprm)
 229 {
 230 }
 231
 232 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 233                 struct page *page)
 234 {
 235         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 236 }
 237
 238 static int __bprm_mm_init(struct linux_binprm *bprm)
 239 {
 240         int err;
 241         struct vm_area_struct *vma = NULL;
 242         struct mm_struct *mm = bprm->mm;
 243
 244         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 245         if (!vma)
 246                 return -ENOMEM;
 247
 248         down_write(&mm->mmap_sem);
 249         vma->vm_mm = mm;
 250
 251         /*
 252          * Place the stack at the largest stack address the architecture
 253          * supports. Later, we'll move this to an appropriate place. We don't
 254          * use STACK_TOP because that can depend on attributes which aren't
 255          * configured yet.
 256          */
 257         vma->vm_end = STACK_TOP_MAX;
 258         vma->vm_start = vma->vm_end - PAGE_SIZE;
 259         vma->vm_flags = VM_STACK_FLAGS;
 260         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 261         err = insert_vm_struct(mm, vma);
 262         if (err)
 263                 goto err;
 264
 265         mm->stack_vm = mm->total_vm = 1;
 266         up_write(&mm->mmap_sem);
 267         bprm->p = vma->vm_end - sizeof(void *);
 268         return 0;
 269 err:
 270         up_write(&mm->mmap_sem);
 271         bprm->vma = NULL;
 272         kmem_cache_free(vm_area_cachep, vma);
 273         return err;
 274 }
 275
 276 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 277 {
 278         return len <= MAX_ARG_STRLEN;
 279 }
 280
 281 #else
 282
 283 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 284                 int write)
 285 {
 286         struct page *page;
 287
 288         page = bprm->page[pos / PAGE_SIZE];
 289         if (!page && write) {
 290                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 291                 if (!page)
 292                         return NULL;
 293                 bprm->page[pos / PAGE_SIZE] = page;
 294         }
 295
 296         return page;
 297 }
 298
 299 static void put_arg_page(struct page *page)
 300 {
 301 }
 302
 303 static void free_arg_page(struct linux_binprm *bprm, int i)
 304 {
 305         if (bprm->page[i]) {
 306                 __free_page(bprm->page[i]);
 307                 bprm->page[i] = NULL;
 308         }
 309 }
 310
 311 static void free_arg_pages(struct linux_binprm *bprm)
 312 {
 313         int i;
 314
 315         for (i = 0; i < MAX_ARG_PAGES; i++)
 316                 free_arg_page(bprm, i);
 317 }
 318
 319 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 320                 struct page *page)
 321 {
 322 }
 323
 324 static int __bprm_mm_init(struct linux_binprm *bprm)
 325 {
 326         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 327         return 0;
 328 }
 329
 330 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 331 {
 332         return len <= bprm->p;
 333 }
 334
 335 #endif /* CONFIG_MMU */
 336
 337 /*
 338  * Create a new mm_struct and populate it with a temporary stack
 339  * vm_area_struct.  We don't have enough context at this point to set the stack
 340  * flags, permissions, and offset, so we use temporary values.  We'll update
 341  * them later in setup_arg_pages().
 342  */
 343 int bprm_mm_init(struct linux_binprm *bprm)
 344 {
 345         int err;
 346         struct mm_struct *mm = NULL;
 347
 348         bprm->mm = mm = mm_alloc();
 349         err = -ENOMEM;
 350         if (!mm)
 351                 goto err;
 352
 353         err = init_new_context(current, mm);
 354         if (err)
 355                 goto err;
 356
 357         err = __bprm_mm_init(bprm);
 358         if (err)
 359                 goto err;
 360
 361         return 0;
 362
 363 err:
 364         if (mm) {
 365                 bprm->mm = NULL;
 366                 mmdrop(mm);
 367         }
 368
 369         return err;
 370 }
 371
 372 /*
 373  * count() counts the number of strings in array ARGV.
 374  */
 375 static int count(char __user * __user * argv, int max)
 376 {
 377         int i = 0;
 378
 379         if (argv != NULL) {
 380                 for (;;) {
 381                         char __user * p;
 382
 383                         if (get_user(p, argv))
 384                                 return -EFAULT;
 385                         if (!p)
 386                                 break;
 387                         argv++;
 388                         if (i++ >= max)
 389                                 return -E2BIG;
 390                         cond_resched();
 391                 }
 392         }
 393         return i;
 394 }
 395
 396 /*
 397  * 'copy_strings()' copies argument/environment strings from the old
 398  * processes's memory to the new process's stack.  The call to get_user_pages()
 399  * ensures the destination page is created and not swapped out.
 400  */
 401 static int copy_strings(int argc, char __user * __user * argv,
 402                         struct linux_binprm *bprm)
 403 {
 404         struct page *kmapped_page = NULL;
 405         char *kaddr = NULL;
 406         unsigned long kpos = 0;
 407         int ret;
 408
 409         while (argc-- > 0) {
 410                 char __user *str;
 411                 int len;
 412                 unsigned long pos;
 413
 414                 if (get_user(str, argv+argc) ||
 415                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 416                         ret = -EFAULT;
 417                         goto out;
 418                 }
 419
 420                 if (!valid_arg_len(bprm, len)) {
 421                         ret = -E2BIG;
 422                         goto out;
 423                 }
 424
 425                 /* We're going to work our way backwords. */
 426                 pos = bprm->p;
 427                 str += len;
 428                 bprm->p -= len;
 429
 430                 while (len > 0) {
 431                         int offset, bytes_to_copy;
 432
 433                         offset = pos % PAGE_SIZE;
 434                         if (offset == 0)
 435                                 offset = PAGE_SIZE;
 436
 437                         bytes_to_copy = offset;
 438                         if (bytes_to_copy > len)
 439                                 bytes_to_copy = len;
 440
 441                         offset -= bytes_to_copy;
 442                         pos -= bytes_to_copy;
 443                         str -= bytes_to_copy;
 444                         len -= bytes_to_copy;
 445
 446                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 447                                 struct page *page;
 448
 449                                 page = get_arg_page(bprm, pos, 1);
 450                                 if (!page) {
 451                                         ret = -E2BIG;
 452                                         goto out;
 453                                 }
 454
 455                                 if (kmapped_page) {
 456                                         flush_kernel_dcache_page(kmapped_page);
 457                                         kunmap(kmapped_page);
 458                                         put_arg_page(kmapped_page);
 459                                 }
 460                                 kmapped_page = page;
 461                                 kaddr = kmap(kmapped_page);
 462                                 kpos = pos & PAGE_MASK;
 463                                 flush_arg_page(bprm, kpos, kmapped_page);
 464                         }
 465                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 466                                 ret = -EFAULT;
 467                                 goto out;
 468                         }
 469                 }
 470         }
 471         ret = 0;
 472 out:
 473         if (kmapped_page) {
 474                 flush_kernel_dcache_page(kmapped_page);
 475                 kunmap(kmapped_page);
 476                 put_arg_page(kmapped_page);
 477         }
 478         return ret;
 479 }
 480
 481 /*
 482  * Like copy_strings, but get argv and its values from kernel memory.
 483  */
 484 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 485 {
 486         int r;
 487         mm_segment_t oldfs = get_fs();
 488         set_fs(KERNEL_DS);
 489         r = copy_strings(argc, (char __user * __user *)argv, bprm);
 490         set_fs(oldfs);
 491         return r;
 492 }
 493 EXPORT_SYMBOL(copy_strings_kernel);
 494
 495 #ifdef CONFIG_MMU
 496
 497 /*
 498  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 499  * the binfmt code determines where the new stack should reside, we shift it to
 500  * its final location.  The process proceeds as follows:
 501  *
 502  * 1) Use shift to calculate the new vma endpoints.
 503  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 504  *    arguments passed to subsequent functions are consistent.
 505  * 3) Move vma's page tables to the new range.
 506  * 4) Free up any cleared pgd range.
 507  * 5) Shrink the vma to cover only the new range.
 508  */
 509 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 510 {
 511         struct mm_struct *mm = vma->vm_mm;
 512         unsigned long old_start = vma->vm_start;
 513         unsigned long old_end = vma->vm_end;
 514         unsigned long length = old_end - old_start;
 515         unsigned long new_start = old_start - shift;
 516         unsigned long new_end = old_end - shift;
 517         struct mmu_gather *tlb;
 518
 519         BUG_ON(new_start > new_end);
 520
 521         /*
 522          * ensure there are no vmas between where we want to go
 523          * and where we are
 524          */
 525         if (vma != find_vma(mm, new_start))
 526                 return -EFAULT;
 527
 528         /*
 529          * cover the whole range: [new_start, old_end)
 530          */
 531         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 532
 533         /*
 534          * move the page tables downwards, on failure we rely on
 535          * process cleanup to remove whatever mess we made.
 536          */
 537         if (length != move_page_tables(vma, old_start,
 538                                        vma, new_start, length))
 539                 return -ENOMEM;
 540
 541         lru_add_drain();
 542         tlb = tlb_gather_mmu(mm, 0);
 543         if (new_end > old_start) {
 544                 /*
 545                  * when the old and new regions overlap clear from new_end.
 546                  */
 547                 free_pgd_range(tlb, new_end, old_end, new_end,
 548                         vma->vm_next ? vma->vm_next->vm_start : 0);
 549         } else {
 550                 /*
 551                  * otherwise, clean from old_start; this is done to not touch
 552                  * the address space in [new_end, old_start) some architectures
 553                  * have constraints on va-space that make this illegal (IA64) -
 554                  * for the others its just a little faster.
 555                  */
 556                 free_pgd_range(tlb, old_start, old_end, new_end,
 557                         vma->vm_next ? vma->vm_next->vm_start : 0);
 558         }
 559         tlb_finish_mmu(tlb, new_end, old_end);
 560
 561         /*
 562          * shrink the vma to just the new range.
 563          */
 564         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 565
 566         return 0;
 567 }
 568
 569 #define EXTRA_STACK_VM_PAGES    20      /* random */
 570
 571 /*
 572  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 573  * the stack is optionally relocated, and some extra space is added.
 574  */
 575 int setup_arg_pages(struct linux_binprm *bprm,
 576                     unsigned long stack_top,
 577                     int executable_stack)
 578 {
 579         unsigned long ret;
 580         unsigned long stack_shift;
 581         struct mm_struct *mm = current->mm;
 582         struct vm_area_struct *vma = bprm->vma;
 583         struct vm_area_struct *prev = NULL;
 584         unsigned long vm_flags;
 585         unsigned long stack_base;
 586
 587 #ifdef CONFIG_STACK_GROWSUP
 588         /* Limit stack size to 1GB */
 589         stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
 590         if (stack_base > (1 << 30))
 591                 stack_base = 1 << 30;
 592
 593         /* Make sure we didn't let the argument array grow too large. */
 594         if (vma->vm_end - vma->vm_start > stack_base)
 595                 return -ENOMEM;
 596
 597         stack_base = PAGE_ALIGN(stack_top - stack_base);
 598
 599         stack_shift = vma->vm_start - stack_base;
 600         mm->arg_start = bprm->p - stack_shift;
 601         bprm->p = vma->vm_end - stack_shift;
 602 #else
 603         stack_top = arch_align_stack(stack_top);
 604         stack_top = PAGE_ALIGN(stack_top);
 605         stack_shift = vma->vm_end - stack_top;
 606
 607         bprm->p -= stack_shift;
 608         mm->arg_start = bprm->p;
 609 #endif
 610
 611         if (bprm->loader)
 612                 bprm->loader -= stack_shift;
 613         bprm->exec -= stack_shift;
 614
 615         down_write(&mm->mmap_sem);
 616         vm_flags = VM_STACK_FLAGS;
 617
 618         /*
 619          * Adjust stack execute permissions; explicitly enable for
 620          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 621          * (arch default) otherwise.
 622          */
 623         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 624                 vm_flags |= VM_EXEC;
 625         else if (executable_stack == EXSTACK_DISABLE_X)
 626                 vm_flags &= ~VM_EXEC;
 627         vm_flags |= mm->def_flags;
 628
 629         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 630                         vm_flags);
 631         if (ret)
 632                 goto out_unlock;
 633         BUG_ON(prev != vma);
 634
 635         /* Move stack pages down in memory. */
 636         if (stack_shift) {
 637                 ret = shift_arg_pages(vma, stack_shift);
 638                 if (ret) {
 639                         up_write(&mm->mmap_sem);
 640                         return ret;
 641                 }
 642         }
 643
 644 #ifdef CONFIG_STACK_GROWSUP
 645         stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 646 #else
 647         stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 648 #endif
 649         ret = expand_stack(vma, stack_base);
 650         if (ret)
 651                 ret = -EFAULT;
 652
 653 out_unlock:
 654         up_write(&mm->mmap_sem);
 655         return 0;
 656 }
 657 EXPORT_SYMBOL(setup_arg_pages);
 658
 659 #endif /* CONFIG_MMU */
 660
 661 struct file *open_exec(const char *name)
 662 {
 663         struct nameidata nd;
 664         struct file *file;
 665         int err;
 666
 667         err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd,
 668                                 FMODE_READ|FMODE_EXEC);
 669         if (err)
 670                 goto out;
 671
 672         err = -EACCES;
 673         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 674                 goto out_path_put;
 675
 676         if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 677                 goto out_path_put;
 678
 679         err = inode_permission(nd.path.dentry->d_inode, MAY_EXEC | MAY_OPEN);
 680         if (err)
 681                 goto out_path_put;
 682         err = ima_path_check(&nd.path, MAY_EXEC | MAY_OPEN);
 683         if (err)
 684                 goto out_path_put;
 685
 686         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 687         if (IS_ERR(file))
 688                 return file;
 689
 690         fsnotify_open(file->f_path.dentry);
 691
 692         err = deny_write_access(file);
 693         if (err) {
 694                 fput(file);
 695                 goto out;
 696         }
 697
 698         return file;
 699
 700  out_path_put:
 701         release_open_intent(&nd);
 702         path_put(&nd.path);
 703  out:
 704         return ERR_PTR(err);
 705 }
 706 EXPORT_SYMBOL(open_exec);
 707
 708 int kernel_read(struct file *file, unsigned long offset,
 709         char *addr, unsigned long count)
 710 {
 711         mm_segment_t old_fs;
 712         loff_t pos = offset;
 713         int result;
 714
 715         old_fs = get_fs();
 716         set_fs(get_ds());
 717         /* The cast to a user pointer is valid due to the set_fs() */
 718         result = vfs_read(file, (void __user *)addr, count, &pos);
 719         set_fs(old_fs);
 720         return result;
 721 }
 722
 723 EXPORT_SYMBOL(kernel_read);
 724
 725 static int exec_mmap(struct mm_struct *mm)
 726 {
 727         struct task_struct *tsk;
 728         struct mm_struct * old_mm, *active_mm;
 729
 730         /* Notify parent that we're no longer interested in the old VM */
 731         tsk = current;
 732         old_mm = current->mm;
 733         mm_release(tsk, old_mm);
 734
 735         if (old_mm) {
 736                 /*
 737                  * Make sure that if there is a core dump in progress
 738                  * for the old mm, we get out and die instead of going
 739                  * through with the exec.  We must hold mmap_sem around
 740                  * checking core_state and changing tsk->mm.
 741                  */
 742                 down_read(&old_mm->mmap_sem);
 743                 if (unlikely(old_mm->core_state)) {
 744                         up_read(&old_mm->mmap_sem);
 745                         return -EINTR;
 746                 }
 747         }
 748         task_lock(tsk);
 749         active_mm = tsk->active_mm;
 750         tsk->mm = mm;
 751         tsk->active_mm = mm;
 752         activate_mm(active_mm, mm);
 753         task_unlock(tsk);
 754         arch_pick_mmap_layout(mm);
 755         if (old_mm) {
 756                 up_read(&old_mm->mmap_sem);
 757                 BUG_ON(active_mm != old_mm);
 758                 mm_update_next_owner(old_mm);
 759                 mmput(old_mm);
 760                 return 0;
 761         }
 762         mmdrop(active_mm);
 763         return 0;
 764 }
 765
 766 /*
 767  * This function makes sure the current process has its own signal table,
 768  * so that flush_signal_handlers can later reset the handlers without
 769  * disturbing other processes.  (Other processes might share the signal
 770  * table via the CLONE_SIGHAND option to clone().)
 771  */
 772 static int de_thread(struct task_struct *tsk)
 773 {
 774         struct signal_struct *sig = tsk->signal;
 775         struct sighand_struct *oldsighand = tsk->sighand;
 776         spinlock_t *lock = &oldsighand->siglock;
 777         int count;
 778
 779         if (thread_group_empty(tsk))
 780                 goto no_thread_group;
 781
 782         /*
 783          * Kill all other threads in the thread group.
 784          */
 785         spin_lock_irq(lock);
 786         if (signal_group_exit(sig)) {
 787                 /*
 788                  * Another group action in progress, just
 789                  * return so that the signal is processed.
 790                  */
 791                 spin_unlock_irq(lock);
 792                 return -EAGAIN;
 793         }
 794         sig->group_exit_task = tsk;
 795         zap_other_threads(tsk);
 796
 797         /* Account for the thread group leader hanging around: */
 798         count = thread_group_leader(tsk) ? 1 : 2;
 799         sig->notify_count = count;
 800         while (atomic_read(&sig->count) > count) {
 801                 __set_current_state(TASK_UNINTERRUPTIBLE);
 802                 spin_unlock_irq(lock);
 803                 schedule();
 804                 spin_lock_irq(lock);
 805         }
 806         spin_unlock_irq(lock);
 807
 808         /*
 809          * At this point all other threads have exited, all we have to
 810          * do is to wait for the thread group leader to become inactive,
 811          * and to assume its PID:
 812          */
 813         if (!thread_group_leader(tsk)) {
 814                 struct task_struct *leader = tsk->group_leader;
 815
 816                 sig->notify_count = -1; /* for exit_notify() */
 817                 for (;;) {
 818                         write_lock_irq(&tasklist_lock);
 819                         if (likely(leader->exit_state))
 820                                 break;
 821                         __set_current_state(TASK_UNINTERRUPTIBLE);
 822                         write_unlock_irq(&tasklist_lock);
 823                         schedule();
 824                 }
 825
 826                 /*
 827                  * The only record we have of the real-time age of a
 828                  * process, regardless of execs it's done, is start_time.
 829                  * All the past CPU time is accumulated in signal_struct
 830                  * from sister threads now dead.  But in this non-leader
 831                  * exec, nothing survives from the original leader thread,
 832                  * whose birth marks the true age of this process now.
 833                  * When we take on its identity by switching to its PID, we
 834                  * also take its birthdate (always earlier than our own).
 835                  */
 836                 tsk->start_time = leader->start_time;
 837
 838                 BUG_ON(!same_thread_group(leader, tsk));
 839                 BUG_ON(has_group_leader_pid(tsk));
 840                 /*
 841                  * An exec() starts a new thread group with the
 842                  * TGID of the previous thread group. Rehash the
 843                  * two threads with a switched PID, and release
 844                  * the former thread group leader:
 845                  */
 846
 847                 /* Become a process group leader with the old leader's pid.
 848                  * The old leader becomes a thread of the this thread group.
 849                  * Note: The old leader also uses this pid until release_task
 850                  *       is called.  Odd but simple and correct.
 851                  */
 852                 detach_pid(tsk, PIDTYPE_PID);
 853                 tsk->pid = leader->pid;
 854                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 855                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 856                 transfer_pid(leader, tsk, PIDTYPE_SID);
 857                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 858
 859                 tsk->group_leader = tsk;
 860                 leader->group_leader = tsk;
 861
 862                 tsk->exit_signal = SIGCHLD;
 863
 864                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 865                 leader->exit_state = EXIT_DEAD;
 866                 write_unlock_irq(&tasklist_lock);
 867
 868                 release_task(leader);
 869         }
 870
 871         sig->group_exit_task = NULL;
 872         sig->notify_count = 0;
 873
 874 no_thread_group:
 875         exit_itimers(sig);
 876         flush_itimer_signals();
 877
 878         if (atomic_read(&oldsighand->count) != 1) {
 879                 struct sighand_struct *newsighand;
 880                 /*
 881                  * This ->sighand is shared with the CLONE_SIGHAND
 882                  * but not CLONE_THREAD task, switch to the new one.
 883                  */
 884                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 885                 if (!newsighand)
 886                         return -ENOMEM;
 887
 888                 atomic_set(&newsighand->count, 1);
 889                 memcpy(newsighand->action, oldsighand->action,
 890                        sizeof(newsighand->action));
 891
 892                 write_lock_irq(&tasklist_lock);
 893                 spin_lock(&oldsighand->siglock);
 894                 rcu_assign_pointer(tsk->sighand, newsighand);
 895                 spin_unlock(&oldsighand->siglock);
 896                 write_unlock_irq(&tasklist_lock);
 897
 898                 __cleanup_sighand(oldsighand);
 899         }
 900
 901         BUG_ON(!thread_group_leader(tsk));
 902         return 0;
 903 }
 904
 905 /*
 906  * These functions flushes out all traces of the currently running executable
 907  * so that a new one can be started
 908  */
 909 static void flush_old_files(struct files_struct * files)
 910 {
 911         long j = -1;
 912         struct fdtable *fdt;
 913
 914         spin_lock(&files->file_lock);
 915         for (;;) {
 916                 unsigned long set, i;
 917
 918                 j++;
 919                 i = j * __NFDBITS;
 920                 fdt = files_fdtable(files);
 921                 if (i >= fdt->max_fds)
 922                         break;
 923                 set = fdt->close_on_exec->fds_bits[j];
 924                 if (!set)
 925                         continue;
 926                 fdt->close_on_exec->fds_bits[j] = 0;
 927                 spin_unlock(&files->file_lock);
 928                 for ( ; set ; i++,set >>= 1) {
 929                         if (set & 1) {
 930                                 sys_close(i);
 931                         }
 932                 }
 933                 spin_lock(&files->file_lock);
 934
 935         }
 936         spin_unlock(&files->file_lock);
 937 }
 938
 939 char *get_task_comm(char *buf, struct task_struct *tsk)
 940 {
 941         /* buf must be at least sizeof(tsk->comm) in size */
 942         task_lock(tsk);
 943         strncpy(buf, tsk->comm, sizeof(tsk->comm));
 944         task_unlock(tsk);
 945         return buf;
 946 }
 947
 948 void set_task_comm(struct task_struct *tsk, char *buf)
 949 {
 950         task_lock(tsk);
 951         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 952         task_unlock(tsk);
 953 }
 954
 955 int flush_old_exec(struct linux_binprm * bprm)
 956 {
 957         char * name;
 958         int i, ch, retval;
 959         char tcomm[sizeof(current->comm)];
 960
 961         /*
 962          * Make sure we have a private signal table and that
 963          * we are unassociated from the previous thread group.
 964          */
 965         retval = de_thread(current);
 966         if (retval)
 967                 goto out;
 968
 969         set_mm_exe_file(bprm->mm, bprm->file);
 970
 971         /*
 972          * Release all of the old mmap stuff
 973          */
 974         retval = exec_mmap(bprm->mm);
 975         if (retval)
 976                 goto out;
 977
 978         bprm->mm = NULL;                /* We're using it now */
 979
 980         /* This is the point of no return */
 981         current->sas_ss_sp = current->sas_ss_size = 0;
 982
 983         if (current_euid() == current_uid() && current_egid() == current_gid())
 984                 set_dumpable(current->mm, 1);
 985         else
 986                 set_dumpable(current->mm, suid_dumpable);
 987
 988         name = bprm->filename;
 989
 990         /* Copies the binary name from after last slash */
 991         for (i=0; (ch = *(name++)) != '\0';) {
 992                 if (ch == '/')
 993                         i = 0; /* overwrite what we wrote */
 994                 else
 995                         if (i < (sizeof(tcomm) - 1))
 996                                 tcomm[i++] = ch;
 997         }
 998         tcomm[i] = '\0';
 999         set_task_comm(current, tcomm);
1000
1001         current->flags &= ~PF_RANDOMIZE;
1002         flush_thread();
1003
1004         /* Set the new mm task size. We have to do that late because it may
1005          * depend on TIF_32BIT which is only updated in flush_thread() on
1006          * some architectures like powerpc
1007          */
1008         current->mm->task_size = TASK_SIZE;
1009
1010         /* install the new credentials */
1011         if (bprm->cred->uid != current_euid() ||
1012             bprm->cred->gid != current_egid()) {
1013                 current->pdeath_signal = 0;
1014         } else if (file_permission(bprm->file, MAY_READ) ||
1015                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1016                 set_dumpable(current->mm, suid_dumpable);
1017         }
1018
1019         current->personality &= ~bprm->per_clear;
1020
1021         /* An exec changes our domain. We are no longer part of the thread
1022            group */
1023
1024         current->self_exec_id++;
1025
1026         flush_signal_handlers(current, 0);
1027         flush_old_files(current->files);
1028
1029         return 0;
1030
1031 out:
1032         return retval;
1033 }
1034
1035 EXPORT_SYMBOL(flush_old_exec);
1036
1037 /*
1038  * install the new credentials for this executable
1039  */
1040 void install_exec_creds(struct linux_binprm *bprm)
1041 {
1042         security_bprm_committing_creds(bprm);
1043
1044         commit_creds(bprm->cred);
1045         bprm->cred = NULL;
1046
1047         /* cred_exec_mutex must be held at least to this point to prevent
1048          * ptrace_attach() from altering our determination of the task's
1049          * credentials; any time after this it may be unlocked */
1050
1051         security_bprm_committed_creds(bprm);
1052 }
1053 EXPORT_SYMBOL(install_exec_creds);
1054
1055 /*
1056  * determine how safe it is to execute the proposed program
1057  * - the caller must hold current->cred_exec_mutex to protect against
1058  *   PTRACE_ATTACH
1059  */
1060 int check_unsafe_exec(struct linux_binprm *bprm)
1061 {
1062         struct task_struct *p = current, *t;
1063         unsigned n_fs;
1064         int res = 0;
1065
1066         bprm->unsafe = tracehook_unsafe_exec(p);
1067
1068         n_fs = 1;
1069         write_lock(&p->fs->lock);
1070         rcu_read_lock();
1071         for (t = next_thread(p); t != p; t = next_thread(t)) {
1072                 if (t->fs == p->fs)
1073                         n_fs++;
1074         }
1075         rcu_read_unlock();
1076
1077         if (p->fs->users > n_fs) {
1078                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1079         } else {
1080                 res = -EAGAIN;
1081                 if (!p->fs->in_exec) {
1082                         p->fs->in_exec = 1;
1083                         res = 1;
1084                 }
1085         }
1086         write_unlock(&p->fs->lock);
1087
1088         return res;
1089 }
1090
1091 /*
1092  * Fill the binprm structure from the inode.
1093  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1094  *
1095  * This may be called multiple times for binary chains (scripts for example).
1096  */
1097 int prepare_binprm(struct linux_binprm *bprm)
1098 {
1099         umode_t mode;
1100         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1101         int retval;
1102
1103         mode = inode->i_mode;
1104         if (bprm->file->f_op == NULL)
1105                 return -EACCES;
1106
1107         /* clear any previous set[ug]id data from a previous binary */
1108         bprm->cred->euid = current_euid();
1109         bprm->cred->egid = current_egid();
1110
1111         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1112                 /* Set-uid? */
1113                 if (mode & S_ISUID) {
1114                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1115                         bprm->cred->euid = inode->i_uid;
1116                 }
1117
1118                 /* Set-gid? */
1119                 /*
1120                  * If setgid is set but no group execute bit then this
1121                  * is a candidate for mandatory locking, not a setgid
1122                  * executable.
1123                  */
1124                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1125                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1126                         bprm->cred->egid = inode->i_gid;
1127                 }
1128         }
1129
1130         /* fill in binprm security blob */
1131         retval = security_bprm_set_creds(bprm);
1132         if (retval)
1133                 return retval;
1134         bprm->cred_prepared = 1;
1135
1136         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1137         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1138 }
1139
1140 EXPORT_SYMBOL(prepare_binprm);
1141
1142 /*
1143  * Arguments are '\0' separated strings found at the location bprm->p
1144  * points to; chop off the first by relocating brpm->p to right after
1145  * the first '\0' encountered.
1146  */
1147 int remove_arg_zero(struct linux_binprm *bprm)
1148 {
1149         int ret = 0;
1150         unsigned long offset;
1151         char *kaddr;
1152         struct page *page;
1153
1154         if (!bprm->argc)
1155                 return 0;
1156
1157         do {
1158                 offset = bprm->p & ~PAGE_MASK;
1159                 page = get_arg_page(bprm, bprm->p, 0);
1160                 if (!page) {
1161                         ret = -EFAULT;
1162                         goto out;
1163                 }
1164                 kaddr = kmap_atomic(page, KM_USER0);
1165
1166                 for (; offset < PAGE_SIZE && kaddr[offset];
1167                                 offset++, bprm->p++)
1168                         ;
1169
1170                 kunmap_atomic(kaddr, KM_USER0);
1171                 put_arg_page(page);
1172
1173                 if (offset == PAGE_SIZE)
1174                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1175         } while (offset == PAGE_SIZE);
1176
1177         bprm->p++;
1178         bprm->argc--;
1179         ret = 0;
1180
1181 out:
1182         return ret;
1183 }
1184 EXPORT_SYMBOL(remove_arg_zero);
1185
1186 /*
1187  * cycle the list of binary formats handler, until one recognizes the image
1188  */
1189 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1190 {
1191         unsigned int depth = bprm->recursion_depth;
1192         int try,retval;
1193         struct linux_binfmt *fmt;
1194
1195         retval = security_bprm_check(bprm);
1196         if (retval)
1197                 return retval;
1198         retval = ima_bprm_check(bprm);
1199         if (retval)
1200                 return retval;
1201
1202         /* kernel module loader fixup */
1203         /* so we don't try to load run modprobe in kernel space. */
1204         set_fs(USER_DS);
1205
1206         retval = audit_bprm(bprm);
1207         if (retval)
1208                 return retval;
1209
1210         retval = -ENOENT;
1211         for (try=0; try<2; try++) {
1212                 read_lock(&binfmt_lock);
1213                 list_for_each_entry(fmt, &formats, lh) {
1214                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1215                         if (!fn)
1216                                 continue;
1217                         if (!try_module_get(fmt->module))
1218                                 continue;
1219                         read_unlock(&binfmt_lock);
1220                         retval = fn(bprm, regs);
1221                         /*
1222                          * Restore the depth counter to its starting value
1223                          * in this call, so we don't have to rely on every
1224                          * load_binary function to restore it on return.
1225                          */
1226                         bprm->recursion_depth = depth;
1227                         if (retval >= 0) {
1228                                 if (depth == 0)
1229                                         tracehook_report_exec(fmt, bprm, regs);
1230                                 put_binfmt(fmt);
1231                                 allow_write_access(bprm->file);
1232                                 if (bprm->file)
1233                                         fput(bprm->file);
1234                                 bprm->file = NULL;
1235                                 current->did_exec = 1;
1236                                 proc_exec_connector(current);
1237                                 return retval;
1238                         }
1239                         read_lock(&binfmt_lock);
1240                         put_binfmt(fmt);
1241                         if (retval != -ENOEXEC || bprm->mm == NULL)
1242                                 break;
1243                         if (!bprm->file) {
1244                                 read_unlock(&binfmt_lock);
1245                                 return retval;
1246                         }
1247                 }
1248                 read_unlock(&binfmt_lock);
1249                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1250                         break;
1251 #ifdef CONFIG_MODULES
1252                 } else {
1253 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1254                         if (printable(bprm->buf[0]) &&
1255                             printable(bprm->buf[1]) &&
1256                             printable(bprm->buf[2]) &&
1257                             printable(bprm->buf[3]))
1258                                 break; /* -ENOEXEC */
1259                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1260 #endif
1261                 }
1262         }
1263         return retval;
1264 }
1265
1266 EXPORT_SYMBOL(search_binary_handler);
1267
1268 void free_bprm(struct linux_binprm *bprm)
1269 {
1270         free_arg_pages(bprm);
1271         if (bprm->cred)
1272                 abort_creds(bprm->cred);
1273         kfree(bprm);
1274 }
1275
1276 /*
1277  * sys_execve() executes a new program.
1278  */
1279 int do_execve(char * filename,
1280         char __user *__user *argv,
1281         char __user *__user *envp,
1282         struct pt_regs * regs)
1283 {
1284         struct linux_binprm *bprm;
1285         struct file *file;
1286         struct files_struct *displaced;
1287         bool clear_in_exec;
1288         int retval;
1289
1290         retval = unshare_files(&displaced);
1291         if (retval)
1292                 goto out_ret;
1293
1294         retval = -ENOMEM;
1295         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1296         if (!bprm)
1297                 goto out_files;
1298
1299         retval = mutex_lock_interruptible(&current->cred_exec_mutex);
1300         if (retval < 0)
1301                 goto out_free;
1302         current->in_execve = 1;
1303
1304         retval = -ENOMEM;
1305         bprm->cred = prepare_exec_creds();
1306         if (!bprm->cred)
1307                 goto out_unlock;
1308
1309         retval = check_unsafe_exec(bprm);
1310         if (retval < 0)
1311                 goto out_unlock;
1312         clear_in_exec = retval;
1313
1314         file = open_exec(filename);
1315         retval = PTR_ERR(file);
1316         if (IS_ERR(file))
1317                 goto out_unmark;
1318
1319         sched_exec();
1320
1321         bprm->file = file;
1322         bprm->filename = filename;
1323         bprm->interp = filename;
1324
1325         retval = bprm_mm_init(bprm);
1326         if (retval)
1327                 goto out_file;
1328
1329         bprm->argc = count(argv, MAX_ARG_STRINGS);
1330         if ((retval = bprm->argc) < 0)
1331                 goto out;
1332
1333         bprm->envc = count(envp, MAX_ARG_STRINGS);
1334         if ((retval = bprm->envc) < 0)
1335                 goto out;
1336
1337         retval = prepare_binprm(bprm);
1338         if (retval < 0)
1339                 goto out;
1340
1341         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1342         if (retval < 0)
1343                 goto out;
1344
1345         bprm->exec = bprm->p;
1346         retval = copy_strings(bprm->envc, envp, bprm);
1347         if (retval < 0)
1348                 goto out;
1349
1350         retval = copy_strings(bprm->argc, argv, bprm);
1351         if (retval < 0)
1352                 goto out;
1353
1354         current->flags &= ~PF_KTHREAD;
1355         retval = search_binary_handler(bprm,regs);
1356         if (retval < 0)
1357                 goto out;
1358
1359         /* execve succeeded */
1360         current->fs->in_exec = 0;
1361         current->in_execve = 0;
1362         mutex_unlock(&current->cred_exec_mutex);
1363         acct_update_integrals(current);
1364         free_bprm(bprm);
1365         if (displaced)
1366                 put_files_struct(displaced);
1367         return retval;
1368
1369 out:
1370         if (bprm->mm)
1371                 mmput (bprm->mm);
1372
1373 out_file:
1374         if (bprm->file) {
1375                 allow_write_access(bprm->file);
1376                 fput(bprm->file);
1377         }
1378
1379 out_unmark:
1380         if (clear_in_exec)
1381                 current->fs->in_exec = 0;
1382
1383 out_unlock:
1384         current->in_execve = 0;
1385         mutex_unlock(&current->cred_exec_mutex);
1386
1387 out_free:
1388         free_bprm(bprm);
1389
1390 out_files:
1391         if (displaced)
1392                 reset_files_struct(displaced);
1393 out_ret:
1394         return retval;
1395 }
1396
1397 int set_binfmt(struct linux_binfmt *new)
1398 {
1399         struct linux_binfmt *old = current->binfmt;
1400
1401         if (new) {
1402                 if (!try_module_get(new->module))
1403                         return -1;
1404         }
1405         current->binfmt = new;
1406         if (old)
1407                 module_put(old->module);
1408         return 0;
1409 }
1410
1411 EXPORT_SYMBOL(set_binfmt);
1412
1413 /* format_corename will inspect the pattern parameter, and output a
1414  * name into corename, which must have space for at least
1415  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1416  */
1417 static int format_corename(char *corename, long signr)
1418 {
1419         const struct cred *cred = current_cred();
1420         const char *pat_ptr = core_pattern;
1421         int ispipe = (*pat_ptr == '|');
1422         char *out_ptr = corename;
1423         char *const out_end = corename + CORENAME_MAX_SIZE;
1424         int rc;
1425         int pid_in_pattern = 0;
1426
1427         /* Repeat as long as we have more pattern to process and more output
1428            space */
1429         while (*pat_ptr) {
1430                 if (*pat_ptr != '%') {
1431                         if (out_ptr == out_end)
1432                                 goto out;
1433                         *out_ptr++ = *pat_ptr++;
1434                 } else {
1435                         switch (*++pat_ptr) {
1436                         case 0:
1437                                 goto out;
1438                         /* Double percent, output one percent */
1439                         case '%':
1440                                 if (out_ptr == out_end)
1441                                         goto out;
1442                                 *out_ptr++ = '%';
1443                                 break;
1444                         /* pid */
1445                         case 'p':
1446                                 pid_in_pattern = 1;
1447                                 rc = snprintf(out_ptr, out_end - out_ptr,
1448                                               "%d", task_tgid_vnr(current));
1449                                 if (rc > out_end - out_ptr)
1450                                         goto out;
1451                                 out_ptr += rc;
1452                                 break;
1453                         /* uid */
1454                         case 'u':
1455                                 rc = snprintf(out_ptr, out_end - out_ptr,
1456                                               "%d", cred->uid);
1457                                 if (rc > out_end - out_ptr)
1458                                         goto out;
1459                                 out_ptr += rc;
1460                                 break;
1461                         /* gid */
1462                         case 'g':
1463                                 rc = snprintf(out_ptr, out_end - out_ptr,
1464                                               "%d", cred->gid);
1465                                 if (rc > out_end - out_ptr)
1466                                         goto out;
1467                                 out_ptr += rc;
1468                                 break;
1469                         /* signal that caused the coredump */
1470                         case 's':
1471                                 rc = snprintf(out_ptr, out_end - out_ptr,
1472                                               "%ld", signr);
1473                                 if (rc > out_end - out_ptr)
1474                                         goto out;
1475                                 out_ptr += rc;
1476                                 break;
1477                         /* UNIX time of coredump */
1478                         case 't': {
1479                                 struct timeval tv;
1480                                 do_gettimeofday(&tv);
1481                                 rc = snprintf(out_ptr, out_end - out_ptr,
1482                                               "%lu", tv.tv_sec);
1483                                 if (rc > out_end - out_ptr)
1484                                         goto out;
1485                                 out_ptr += rc;
1486                                 break;
1487                         }
1488                         /* hostname */
1489                         case 'h':
1490                                 down_read(&uts_sem);
1491                                 rc = snprintf(out_ptr, out_end - out_ptr,
1492                                               "%s", utsname()->nodename);
1493                                 up_read(&uts_sem);
1494                                 if (rc > out_end - out_ptr)
1495                                         goto out;
1496                                 out_ptr += rc;
1497                                 break;
1498                         /* executable */
1499                         case 'e':
1500                                 rc = snprintf(out_ptr, out_end - out_ptr,
1501                                               "%s", current->comm);
1502                                 if (rc > out_end - out_ptr)
1503                                         goto out;
1504                                 out_ptr += rc;
1505                                 break;
1506                         /* core limit size */
1507                         case 'c':
1508                                 rc = snprintf(out_ptr, out_end - out_ptr,
1509                                               "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1510                                 if (rc > out_end - out_ptr)
1511                                         goto out;
1512                                 out_ptr += rc;
1513                                 break;
1514                         default:
1515                                 break;
1516                         }
1517                         ++pat_ptr;
1518                 }
1519         }
1520         /* Backward compatibility with core_uses_pid:
1521          *
1522          * If core_pattern does not include a %p (as is the default)
1523          * and core_uses_pid is set, then .%pid will be appended to
1524          * the filename. Do not do this for piped commands. */
1525         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1526                 rc = snprintf(out_ptr, out_end - out_ptr,
1527                               ".%d", task_tgid_vnr(current));
1528                 if (rc > out_end - out_ptr)
1529                         goto out;
1530                 out_ptr += rc;
1531         }
1532 out:
1533         *out_ptr = 0;
1534         return ispipe;
1535 }
1536
1537 static int zap_process(struct task_struct *start)
1538 {
1539         struct task_struct *t;
1540         int nr = 0;
1541
1542         start->signal->flags = SIGNAL_GROUP_EXIT;
1543         start->signal->group_stop_count = 0;
1544
1545         t = start;
1546         do {
1547                 if (t != current && t->mm) {
1548                         sigaddset(&t->pending.signal, SIGKILL);
1549                         signal_wake_up(t, 1);
1550                         nr++;
1551                 }
1552         } while_each_thread(start, t);
1553
1554         return nr;
1555 }
1556
1557 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1558                                 struct core_state *core_state, int exit_code)
1559 {
1560         struct task_struct *g, *p;
1561         unsigned long flags;
1562         int nr = -EAGAIN;
1563
1564         spin_lock_irq(&tsk->sighand->siglock);
1565         if (!signal_group_exit(tsk->signal)) {
1566                 mm->core_state = core_state;
1567                 tsk->signal->group_exit_code = exit_code;
1568                 nr = zap_process(tsk);
1569         }
1570         spin_unlock_irq(&tsk->sighand->siglock);
1571         if (unlikely(nr < 0))
1572                 return nr;
1573
1574         if (atomic_read(&mm->mm_users) == nr + 1)
1575                 goto done;
1576         /*
1577          * We should find and kill all tasks which use this mm, and we should
1578          * count them correctly into ->nr_threads. We don't take tasklist
1579          * lock, but this is safe wrt:
1580          *
1581          * fork:
1582          *      None of sub-threads can fork after zap_process(leader). All
1583          *      processes which were created before this point should be
1584          *      visible to zap_threads() because copy_process() adds the new
1585          *      process to the tail of init_task.tasks list, and lock/unlock
1586          *      of ->siglock provides a memory barrier.
1587          *
1588          * do_exit:
1589          *      The caller holds mm->mmap_sem. This means that the task which
1590          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1591          *      its ->mm.
1592          *
1593          * de_thread:
1594          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1595          *      we must see either old or new leader, this does not matter.
1596          *      However, it can change p->sighand, so lock_task_sighand(p)
1597          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1598          *      it can't fail.
1599          *
1600          *      Note also that "g" can be the old leader with ->mm == NULL
1601          *      and already unhashed and thus removed from ->thread_group.
1602          *      This is OK, __unhash_process()->list_del_rcu() does not
1603          *      clear the ->next pointer, we will find the new leader via
1604          *      next_thread().
1605          */
1606         rcu_read_lock();
1607         for_each_process(g) {
1608                 if (g == tsk->group_leader)
1609                         continue;
1610                 if (g->flags & PF_KTHREAD)
1611                         continue;
1612                 p = g;
1613                 do {
1614                         if (p->mm) {
1615                                 if (unlikely(p->mm == mm)) {
1616                                         lock_task_sighand(p, &flags);
1617                                         nr += zap_process(p);
1618                                         unlock_task_sighand(p, &flags);
1619                                 }
1620                                 break;
1621                         }
1622                 } while_each_thread(g, p);
1623         }
1624         rcu_read_unlock();
1625 done:
1626         atomic_set(&core_state->nr_threads, nr);
1627         return nr;
1628 }
1629
1630 static int coredump_wait(int exit_code, struct core_state *core_state)
1631 {
1632         struct task_struct *tsk = current;
1633         struct mm_struct *mm = tsk->mm;
1634         struct completion *vfork_done;
1635         int core_waiters;
1636
1637         init_completion(&core_state->startup);
1638         core_state->dumper.task = tsk;
1639         core_state->dumper.next = NULL;
1640         core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1641         up_write(&mm->mmap_sem);
1642
1643         if (unlikely(core_waiters < 0))
1644                 goto fail;
1645
1646         /*
1647          * Make sure nobody is waiting for us to release the VM,
1648          * otherwise we can deadlock when we wait on each other
1649          */
1650         vfork_done = tsk->vfork_done;
1651         if (vfork_done) {
1652                 tsk->vfork_done = NULL;
1653                 complete(vfork_done);
1654         }
1655
1656         if (core_waiters)
1657                 wait_for_completion(&core_state->startup);
1658 fail:
1659         return core_waiters;
1660 }
1661
1662 static void coredump_finish(struct mm_struct *mm)
1663 {
1664         struct core_thread *curr, *next;
1665         struct task_struct *task;
1666
1667         next = mm->core_state->dumper.next;
1668         while ((curr = next) != NULL) {
1669                 next = curr->next;
1670                 task = curr->task;
1671                 /*
1672                  * see exit_mm(), curr->task must not see
1673                  * ->task == NULL before we read ->next.
1674                  */
1675                 smp_mb();
1676                 curr->task = NULL;
1677                 wake_up_process(task);
1678         }
1679
1680         mm->core_state = NULL;
1681 }
1682
1683 /*
1684  * set_dumpable converts traditional three-value dumpable to two flags and
1685  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1686  * these bits are not changed atomically.  So get_dumpable can observe the
1687  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1688  * return either old dumpable or new one by paying attention to the order of
1689  * modifying the bits.
1690  *
1691  * dumpable |   mm->flags (binary)
1692  * old  new | initial interim  final
1693  * ---------+-----------------------
1694  *  0    1  |   00      01      01
1695  *  0    2  |   00      10(*)   11
1696  *  1    0  |   01      00      00
1697  *  1    2  |   01      11      11
1698  *  2    0  |   11      10(*)   00
1699  *  2    1  |   11      11      01
1700  *
1701  * (*) get_dumpable regards interim value of 10 as 11.
1702  */
1703 void set_dumpable(struct mm_struct *mm, int value)
1704 {
1705         switch (value) {
1706         case 0:
1707                 clear_bit(MMF_DUMPABLE, &mm->flags);
1708                 smp_wmb();
1709                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1710                 break;
1711         case 1:
1712                 set_bit(MMF_DUMPABLE, &mm->flags);
1713                 smp_wmb();
1714                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1715                 break;
1716         case 2:
1717                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1718                 smp_wmb();
1719                 set_bit(MMF_DUMPABLE, &mm->flags);
1720                 break;
1721         }
1722 }
1723
1724 int get_dumpable(struct mm_struct *mm)
1725 {
1726         int ret;
1727
1728         ret = mm->flags & 0x3;
1729         return (ret >= 2) ? 2 : ret;
1730 }
1731
1732 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1733 {
1734         struct core_state core_state;
1735         char corename[CORENAME_MAX_SIZE + 1];
1736         struct mm_struct *mm = current->mm;
1737         struct linux_binfmt * binfmt;
1738         struct inode * inode;
1739         struct file * file;
1740         const struct cred *old_cred;
1741         struct cred *cred;
1742         int retval = 0;
1743         int flag = 0;
1744         int ispipe = 0;
1745         unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1746         char **helper_argv = NULL;
1747         int helper_argc = 0;
1748         char *delimit;
1749
1750         audit_core_dumps(signr);
1751
1752         binfmt = current->binfmt;
1753         if (!binfmt || !binfmt->core_dump)
1754                 goto fail;
1755
1756         cred = prepare_creds();
1757         if (!cred) {
1758                 retval = -ENOMEM;
1759                 goto fail;
1760         }
1761
1762         down_write(&mm->mmap_sem);
1763         /*
1764          * If another thread got here first, or we are not dumpable, bail out.
1765          */
1766         if (mm->core_state || !get_dumpable(mm)) {
1767                 up_write(&mm->mmap_sem);
1768                 put_cred(cred);
1769                 goto fail;
1770         }
1771
1772         /*
1773          *      We cannot trust fsuid as being the "true" uid of the
1774          *      process nor do we know its entire history. We only know it
1775          *      was tainted so we dump it as root in mode 2.
1776          */
1777         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1778                 flag = O_EXCL;          /* Stop rewrite attacks */
1779                 cred->fsuid = 0;        /* Dump root private */
1780         }
1781
1782         retval = coredump_wait(exit_code, &core_state);
1783         if (retval < 0) {
1784                 put_cred(cred);
1785                 goto fail;
1786         }
1787
1788         old_cred = override_creds(cred);
1789
1790         /*
1791          * Clear any false indication of pending signals that might
1792          * be seen by the filesystem code called to write the core file.
1793          */
1794         clear_thread_flag(TIF_SIGPENDING);
1795
1796         /*
1797          * lock_kernel() because format_corename() is controlled by sysctl, which
1798          * uses lock_kernel()
1799          */
1800         lock_kernel();
1801         ispipe = format_corename(corename, signr);
1802         unlock_kernel();
1803         /*
1804          * Don't bother to check the RLIMIT_CORE value if core_pattern points
1805          * to a pipe.  Since we're not writing directly to the filesystem
1806          * RLIMIT_CORE doesn't really apply, as no actual core file will be
1807          * created unless the pipe reader choses to write out the core file
1808          * at which point file size limits and permissions will be imposed
1809          * as it does with any other process
1810          */
1811         if ((!ispipe) && (core_limit < binfmt->min_coredump))
1812                 goto fail_unlock;
1813
1814         if (ispipe) {
1815                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1816                 if (!helper_argv) {
1817                         printk(KERN_WARNING "%s failed to allocate memory\n",
1818                                __func__);
1819                         goto fail_unlock;
1820                 }
1821                 /* Terminate the string before the first option */
1822                 delimit = strchr(corename, ' ');
1823                 if (delimit)
1824                         *delimit = '\0';
1825                 delimit = strrchr(helper_argv[0], '/');
1826                 if (delimit)
1827                         delimit++;
1828                 else
1829                         delimit = helper_argv[0];
1830                 if (!strcmp(delimit, current->comm)) {
1831                         printk(KERN_NOTICE "Recursive core dump detected, "
1832                                         "aborting\n");
1833                         goto fail_unlock;
1834                 }
1835
1836                 core_limit = RLIM_INFINITY;
1837
1838                 /* SIGPIPE can happen, but it's just never processed */
1839                 if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
1840                                 &file)) {
1841                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1842                                corename);
1843                         goto fail_unlock;
1844                 }
1845         } else
1846                 file = filp_open(corename,
1847                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1848                                  0600);
1849         if (IS_ERR(file))
1850                 goto fail_unlock;
1851         inode = file->f_path.dentry->d_inode;
1852         if (inode->i_nlink > 1)
1853                 goto close_fail;        /* multiple links - don't dump */
1854         if (!ispipe && d_unhashed(file->f_path.dentry))
1855                 goto close_fail;
1856
1857         /* AK: actually i see no reason to not allow this for named pipes etc.,
1858            but keep the previous behaviour for now. */
1859         if (!ispipe && !S_ISREG(inode->i_mode))
1860                 goto close_fail;
1861         /*
1862          * Dont allow local users get cute and trick others to coredump
1863          * into their pre-created files:
1864          */
1865         if (inode->i_uid != current_fsuid())
1866                 goto close_fail;
1867         if (!file->f_op)
1868                 goto close_fail;
1869         if (!file->f_op->write)
1870                 goto close_fail;
1871         if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1872                 goto close_fail;
1873
1874         retval = binfmt->core_dump(signr, regs, file, core_limit);
1875
1876         if (retval)
1877                 current->signal->group_exit_code |= 0x80;
1878 close_fail:
1879         filp_close(file, NULL);
1880 fail_unlock:
1881         if (helper_argv)
1882                 argv_free(helper_argv);
1883
1884         revert_creds(old_cred);
1885         put_cred(cred);
1886         coredump_finish(mm);
1887 fail:
1888         return;
1889 }