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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/highmem.h>
  36 #include <linux/spinlock.h>
  37 #include <linux/key.h>
  38 #include <linux/personality.h>
  39 #include <linux/binfmts.h>
  40 #include <linux/utsname.h>
  41 #include <linux/pid_namespace.h>
  42 #include <linux/module.h>
  43 #include <linux/namei.h>
  44 #include <linux/proc_fs.h>
  45 #include <linux/ptrace.h>
  46 #include <linux/mount.h>
  47 #include <linux/security.h>
  48 #include <linux/syscalls.h>
  49 #include <linux/tsacct_kern.h>
  50 #include <linux/cn_proc.h>
  51 #include <linux/audit.h>
  52
  53 #include <asm/uaccess.h>
  54 #include <asm/mmu_context.h>
  55 #include <asm/tlb.h>
  56
  57 #ifdef CONFIG_KMOD
  58 #include <linux/kmod.h>
  59 #endif
  60
  61 #ifdef __alpha__
  62 /* for /sbin/loader handling in search_binary_handler() */
  63 #include <linux/a.out.h>
  64 #endif
  65
  66 int core_uses_pid;
  67 char core_pattern[CORENAME_MAX_SIZE] = "core";
  68 int suid_dumpable = 0;
  69
  70 /* The maximal length of core_pattern is also specified in sysctl.c */
  71
  72 static LIST_HEAD(formats);
  73 static DEFINE_RWLOCK(binfmt_lock);
  74
  75 int register_binfmt(struct linux_binfmt * fmt)
  76 {
  77         if (!fmt)
  78                 return -EINVAL;
  79         write_lock(&binfmt_lock);
  80         list_add(&fmt->lh, &formats);
  81         write_unlock(&binfmt_lock);
  82         return 0;
  83 }
  84
  85 EXPORT_SYMBOL(register_binfmt);
  86
  87 void unregister_binfmt(struct linux_binfmt * fmt)
  88 {
  89         write_lock(&binfmt_lock);
  90         list_del(&fmt->lh);
  91         write_unlock(&binfmt_lock);
  92 }
  93
  94 EXPORT_SYMBOL(unregister_binfmt);
  95
  96 static inline void put_binfmt(struct linux_binfmt * fmt)
  97 {
  98         module_put(fmt->module);
  99 }
 100
 101 /*
 102  * Note that a shared library must be both readable and executable due to
 103  * security reasons.
 104  *
 105  * Also note that we take the address to load from from the file itself.
 106  */
 107 asmlinkage long sys_uselib(const char __user * library)
 108 {
 109         struct file * file;
 110         struct nameidata nd;
 111         int error;
 112
 113         error = __user_path_lookup_open(library, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
 114         if (error)
 115                 goto out;
 116
 117         error = -EINVAL;
 118         if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 119                 goto exit;
 120
 121         error = vfs_permission(&nd, MAY_READ | MAY_EXEC);
 122         if (error)
 123                 goto exit;
 124
 125         file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 126         error = PTR_ERR(file);
 127         if (IS_ERR(file))
 128                 goto out;
 129
 130         error = -ENOEXEC;
 131         if(file->f_op) {
 132                 struct linux_binfmt * fmt;
 133
 134                 read_lock(&binfmt_lock);
 135                 list_for_each_entry(fmt, &formats, lh) {
 136                         if (!fmt->load_shlib)
 137                                 continue;
 138                         if (!try_module_get(fmt->module))
 139                                 continue;
 140                         read_unlock(&binfmt_lock);
 141                         error = fmt->load_shlib(file);
 142                         read_lock(&binfmt_lock);
 143                         put_binfmt(fmt);
 144                         if (error != -ENOEXEC)
 145                                 break;
 146                 }
 147                 read_unlock(&binfmt_lock);
 148         }
 149         fput(file);
 150 out:
 151         return error;
 152 exit:
 153         release_open_intent(&nd);
 154         path_put(&nd.path);
 155         goto out;
 156 }
 157
 158 #ifdef CONFIG_MMU
 159
 160 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 161                 int write)
 162 {
 163         struct page *page;
 164         int ret;
 165
 166 #ifdef CONFIG_STACK_GROWSUP
 167         if (write) {
 168                 ret = expand_stack_downwards(bprm->vma, pos);
 169                 if (ret < 0)
 170                         return NULL;
 171         }
 172 #endif
 173         ret = get_user_pages(current, bprm->mm, pos,
 174                         1, write, 1, &page, NULL);
 175         if (ret <= 0)
 176                 return NULL;
 177
 178         if (write) {
 179                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 180                 struct rlimit *rlim;
 181
 182                 /*
 183                  * We've historically supported up to 32 pages (ARG_MAX)
 184                  * of argument strings even with small stacks
 185                  */
 186                 if (size <= ARG_MAX)
 187                         return page;
 188
 189                 /*
 190                  * Limit to 1/4-th the stack size for the argv+env strings.
 191                  * This ensures that:
 192                  *  - the remaining binfmt code will not run out of stack space,
 193                  *  - the program will have a reasonable amount of stack left
 194                  *    to work from.
 195                  */
 196                 rlim = current->signal->rlim;
 197                 if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
 198                         put_page(page);
 199                         return NULL;
 200                 }
 201         }
 202
 203         return page;
 204 }
 205
 206 static void put_arg_page(struct page *page)
 207 {
 208         put_page(page);
 209 }
 210
 211 static void free_arg_page(struct linux_binprm *bprm, int i)
 212 {
 213 }
 214
 215 static void free_arg_pages(struct linux_binprm *bprm)
 216 {
 217 }
 218
 219 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 220                 struct page *page)
 221 {
 222         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 223 }
 224
 225 static int __bprm_mm_init(struct linux_binprm *bprm)
 226 {
 227         int err = -ENOMEM;
 228         struct vm_area_struct *vma = NULL;
 229         struct mm_struct *mm = bprm->mm;
 230
 231         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 232         if (!vma)
 233                 goto err;
 234
 235         down_write(&mm->mmap_sem);
 236         vma->vm_mm = mm;
 237
 238         /*
 239          * Place the stack at the largest stack address the architecture
 240          * supports. Later, we'll move this to an appropriate place. We don't
 241          * use STACK_TOP because that can depend on attributes which aren't
 242          * configured yet.
 243          */
 244         vma->vm_end = STACK_TOP_MAX;
 245         vma->vm_start = vma->vm_end - PAGE_SIZE;
 246
 247         vma->vm_flags = VM_STACK_FLAGS;
 248         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 249         err = insert_vm_struct(mm, vma);
 250         if (err) {
 251                 up_write(&mm->mmap_sem);
 252                 goto err;
 253         }
 254
 255         mm->stack_vm = mm->total_vm = 1;
 256         up_write(&mm->mmap_sem);
 257
 258         bprm->p = vma->vm_end - sizeof(void *);
 259
 260         return 0;
 261
 262 err:
 263         if (vma) {
 264                 bprm->vma = NULL;
 265                 kmem_cache_free(vm_area_cachep, vma);
 266         }
 267
 268         return err;
 269 }
 270
 271 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 272 {
 273         return len <= MAX_ARG_STRLEN;
 274 }
 275
 276 #else
 277
 278 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 279                 int write)
 280 {
 281         struct page *page;
 282
 283         page = bprm->page[pos / PAGE_SIZE];
 284         if (!page && write) {
 285                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 286                 if (!page)
 287                         return NULL;
 288                 bprm->page[pos / PAGE_SIZE] = page;
 289         }
 290
 291         return page;
 292 }
 293
 294 static void put_arg_page(struct page *page)
 295 {
 296 }
 297
 298 static void free_arg_page(struct linux_binprm *bprm, int i)
 299 {
 300         if (bprm->page[i]) {
 301                 __free_page(bprm->page[i]);
 302                 bprm->page[i] = NULL;
 303         }
 304 }
 305
 306 static void free_arg_pages(struct linux_binprm *bprm)
 307 {
 308         int i;
 309
 310         for (i = 0; i < MAX_ARG_PAGES; i++)
 311                 free_arg_page(bprm, i);
 312 }
 313
 314 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 315                 struct page *page)
 316 {
 317 }
 318
 319 static int __bprm_mm_init(struct linux_binprm *bprm)
 320 {
 321         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 322         return 0;
 323 }
 324
 325 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 326 {
 327         return len <= bprm->p;
 328 }
 329
 330 #endif /* CONFIG_MMU */
 331
 332 /*
 333  * Create a new mm_struct and populate it with a temporary stack
 334  * vm_area_struct.  We don't have enough context at this point to set the stack
 335  * flags, permissions, and offset, so we use temporary values.  We'll update
 336  * them later in setup_arg_pages().
 337  */
 338 int bprm_mm_init(struct linux_binprm *bprm)
 339 {
 340         int err;
 341         struct mm_struct *mm = NULL;
 342
 343         bprm->mm = mm = mm_alloc();
 344         err = -ENOMEM;
 345         if (!mm)
 346                 goto err;
 347
 348         err = init_new_context(current, mm);
 349         if (err)
 350                 goto err;
 351
 352         err = __bprm_mm_init(bprm);
 353         if (err)
 354                 goto err;
 355
 356         return 0;
 357
 358 err:
 359         if (mm) {
 360                 bprm->mm = NULL;
 361                 mmdrop(mm);
 362         }
 363
 364         return err;
 365 }
 366
 367 /*
 368  * count() counts the number of strings in array ARGV.
 369  */
 370 static int count(char __user * __user * argv, int max)
 371 {
 372         int i = 0;
 373
 374         if (argv != NULL) {
 375                 for (;;) {
 376                         char __user * p;
 377
 378                         if (get_user(p, argv))
 379                                 return -EFAULT;
 380                         if (!p)
 381                                 break;
 382                         argv++;
 383                         if(++i > max)
 384                                 return -E2BIG;
 385                         cond_resched();
 386                 }
 387         }
 388         return i;
 389 }
 390
 391 /*
 392  * 'copy_strings()' copies argument/environment strings from the old
 393  * processes's memory to the new process's stack.  The call to get_user_pages()
 394  * ensures the destination page is created and not swapped out.
 395  */
 396 static int copy_strings(int argc, char __user * __user * argv,
 397                         struct linux_binprm *bprm)
 398 {
 399         struct page *kmapped_page = NULL;
 400         char *kaddr = NULL;
 401         unsigned long kpos = 0;
 402         int ret;
 403
 404         while (argc-- > 0) {
 405                 char __user *str;
 406                 int len;
 407                 unsigned long pos;
 408
 409                 if (get_user(str, argv+argc) ||
 410                                 !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 411                         ret = -EFAULT;
 412                         goto out;
 413                 }
 414
 415                 if (!valid_arg_len(bprm, len)) {
 416                         ret = -E2BIG;
 417                         goto out;
 418                 }
 419
 420                 /* We're going to work our way backwords. */
 421                 pos = bprm->p;
 422                 str += len;
 423                 bprm->p -= len;
 424
 425                 while (len > 0) {
 426                         int offset, bytes_to_copy;
 427
 428                         offset = pos % PAGE_SIZE;
 429                         if (offset == 0)
 430                                 offset = PAGE_SIZE;
 431
 432                         bytes_to_copy = offset;
 433                         if (bytes_to_copy > len)
 434                                 bytes_to_copy = len;
 435
 436                         offset -= bytes_to_copy;
 437                         pos -= bytes_to_copy;
 438                         str -= bytes_to_copy;
 439                         len -= bytes_to_copy;
 440
 441                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 442                                 struct page *page;
 443
 444                                 page = get_arg_page(bprm, pos, 1);
 445                                 if (!page) {
 446                                         ret = -E2BIG;
 447                                         goto out;
 448                                 }
 449
 450                                 if (kmapped_page) {
 451                                         flush_kernel_dcache_page(kmapped_page);
 452                                         kunmap(kmapped_page);
 453                                         put_arg_page(kmapped_page);
 454                                 }
 455                                 kmapped_page = page;
 456                                 kaddr = kmap(kmapped_page);
 457                                 kpos = pos & PAGE_MASK;
 458                                 flush_arg_page(bprm, kpos, kmapped_page);
 459                         }
 460                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 461                                 ret = -EFAULT;
 462                                 goto out;
 463                         }
 464                 }
 465         }
 466         ret = 0;
 467 out:
 468         if (kmapped_page) {
 469                 flush_kernel_dcache_page(kmapped_page);
 470                 kunmap(kmapped_page);
 471                 put_arg_page(kmapped_page);
 472         }
 473         return ret;
 474 }
 475
 476 /*
 477  * Like copy_strings, but get argv and its values from kernel memory.
 478  */
 479 int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 480 {
 481         int r;
 482         mm_segment_t oldfs = get_fs();
 483         set_fs(KERNEL_DS);
 484         r = copy_strings(argc, (char __user * __user *)argv, bprm);
 485         set_fs(oldfs);
 486         return r;
 487 }
 488 EXPORT_SYMBOL(copy_strings_kernel);
 489
 490 #ifdef CONFIG_MMU
 491
 492 /*
 493  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 494  * the binfmt code determines where the new stack should reside, we shift it to
 495  * its final location.  The process proceeds as follows:
 496  *
 497  * 1) Use shift to calculate the new vma endpoints.
 498  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 499  *    arguments passed to subsequent functions are consistent.
 500  * 3) Move vma's page tables to the new range.
 501  * 4) Free up any cleared pgd range.
 502  * 5) Shrink the vma to cover only the new range.
 503  */
 504 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 505 {
 506         struct mm_struct *mm = vma->vm_mm;
 507         unsigned long old_start = vma->vm_start;
 508         unsigned long old_end = vma->vm_end;
 509         unsigned long length = old_end - old_start;
 510         unsigned long new_start = old_start - shift;
 511         unsigned long new_end = old_end - shift;
 512         struct mmu_gather *tlb;
 513
 514         BUG_ON(new_start > new_end);
 515
 516         /*
 517          * ensure there are no vmas between where we want to go
 518          * and where we are
 519          */
 520         if (vma != find_vma(mm, new_start))
 521                 return -EFAULT;
 522
 523         /*
 524          * cover the whole range: [new_start, old_end)
 525          */
 526         vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 527
 528         /*
 529          * move the page tables downwards, on failure we rely on
 530          * process cleanup to remove whatever mess we made.
 531          */
 532         if (length != move_page_tables(vma, old_start,
 533                                        vma, new_start, length))
 534                 return -ENOMEM;
 535
 536         lru_add_drain();
 537         tlb = tlb_gather_mmu(mm, 0);
 538         if (new_end > old_start) {
 539                 /*
 540                  * when the old and new regions overlap clear from new_end.
 541                  */
 542                 free_pgd_range(tlb, new_end, old_end, new_end,
 543                         vma->vm_next ? vma->vm_next->vm_start : 0);
 544         } else {
 545                 /*
 546                  * otherwise, clean from old_start; this is done to not touch
 547                  * the address space in [new_end, old_start) some architectures
 548                  * have constraints on va-space that make this illegal (IA64) -
 549                  * for the others its just a little faster.
 550                  */
 551                 free_pgd_range(tlb, old_start, old_end, new_end,
 552                         vma->vm_next ? vma->vm_next->vm_start : 0);
 553         }
 554         tlb_finish_mmu(tlb, new_end, old_end);
 555
 556         /*
 557          * shrink the vma to just the new range.
 558          */
 559         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 560
 561         return 0;
 562 }
 563
 564 #define EXTRA_STACK_VM_PAGES    20      /* random */
 565
 566 /*
 567  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 568  * the stack is optionally relocated, and some extra space is added.
 569  */
 570 int setup_arg_pages(struct linux_binprm *bprm,
 571                     unsigned long stack_top,
 572                     int executable_stack)
 573 {
 574         unsigned long ret;
 575         unsigned long stack_shift;
 576         struct mm_struct *mm = current->mm;
 577         struct vm_area_struct *vma = bprm->vma;
 578         struct vm_area_struct *prev = NULL;
 579         unsigned long vm_flags;
 580         unsigned long stack_base;
 581
 582 #ifdef CONFIG_STACK_GROWSUP
 583         /* Limit stack size to 1GB */
 584         stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
 585         if (stack_base > (1 << 30))
 586                 stack_base = 1 << 30;
 587
 588         /* Make sure we didn't let the argument array grow too large. */
 589         if (vma->vm_end - vma->vm_start > stack_base)
 590                 return -ENOMEM;
 591
 592         stack_base = PAGE_ALIGN(stack_top - stack_base);
 593
 594         stack_shift = vma->vm_start - stack_base;
 595         mm->arg_start = bprm->p - stack_shift;
 596         bprm->p = vma->vm_end - stack_shift;
 597 #else
 598         stack_top = arch_align_stack(stack_top);
 599         stack_top = PAGE_ALIGN(stack_top);
 600         stack_shift = vma->vm_end - stack_top;
 601
 602         bprm->p -= stack_shift;
 603         mm->arg_start = bprm->p;
 604 #endif
 605
 606         if (bprm->loader)
 607                 bprm->loader -= stack_shift;
 608         bprm->exec -= stack_shift;
 609
 610         down_write(&mm->mmap_sem);
 611         vm_flags = VM_STACK_FLAGS;
 612
 613         /*
 614          * Adjust stack execute permissions; explicitly enable for
 615          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 616          * (arch default) otherwise.
 617          */
 618         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 619                 vm_flags |= VM_EXEC;
 620         else if (executable_stack == EXSTACK_DISABLE_X)
 621                 vm_flags &= ~VM_EXEC;
 622         vm_flags |= mm->def_flags;
 623
 624         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 625                         vm_flags);
 626         if (ret)
 627                 goto out_unlock;
 628         BUG_ON(prev != vma);
 629
 630         /* Move stack pages down in memory. */
 631         if (stack_shift) {
 632                 ret = shift_arg_pages(vma, stack_shift);
 633                 if (ret) {
 634                         up_write(&mm->mmap_sem);
 635                         return ret;
 636                 }
 637         }
 638
 639 #ifdef CONFIG_STACK_GROWSUP
 640         stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 641 #else
 642         stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 643 #endif
 644         ret = expand_stack(vma, stack_base);
 645         if (ret)
 646                 ret = -EFAULT;
 647
 648 out_unlock:
 649         up_write(&mm->mmap_sem);
 650         return 0;
 651 }
 652 EXPORT_SYMBOL(setup_arg_pages);
 653
 654 #endif /* CONFIG_MMU */
 655
 656 struct file *open_exec(const char *name)
 657 {
 658         struct nameidata nd;
 659         int err;
 660         struct file *file;
 661
 662         err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
 663         file = ERR_PTR(err);
 664
 665         if (!err) {
 666                 struct inode *inode = nd.path.dentry->d_inode;
 667                 file = ERR_PTR(-EACCES);
 668                 if (S_ISREG(inode->i_mode)) {
 669                         int err = vfs_permission(&nd, MAY_EXEC);
 670                         file = ERR_PTR(err);
 671                         if (!err) {
 672                                 file = nameidata_to_filp(&nd,
 673                                                         O_RDONLY|O_LARGEFILE);
 674                                 if (!IS_ERR(file)) {
 675                                         err = deny_write_access(file);
 676                                         if (err) {
 677                                                 fput(file);
 678                                                 file = ERR_PTR(err);
 679                                         }
 680                                 }
 681 out:
 682                                 return file;
 683                         }
 684                 }
 685                 release_open_intent(&nd);
 686                 path_put(&nd.path);
 687         }
 688         goto out;
 689 }
 690
 691 EXPORT_SYMBOL(open_exec);
 692
 693 int kernel_read(struct file *file, unsigned long offset,
 694         char *addr, unsigned long count)
 695 {
 696         mm_segment_t old_fs;
 697         loff_t pos = offset;
 698         int result;
 699
 700         old_fs = get_fs();
 701         set_fs(get_ds());
 702         /* The cast to a user pointer is valid due to the set_fs() */
 703         result = vfs_read(file, (void __user *)addr, count, &pos);
 704         set_fs(old_fs);
 705         return result;
 706 }
 707
 708 EXPORT_SYMBOL(kernel_read);
 709
 710 static int exec_mmap(struct mm_struct *mm)
 711 {
 712         struct task_struct *tsk;
 713         struct mm_struct * old_mm, *active_mm;
 714
 715         /* Notify parent that we're no longer interested in the old VM */
 716         tsk = current;
 717         old_mm = current->mm;
 718         mm_release(tsk, old_mm);
 719
 720         if (old_mm) {
 721                 /*
 722                  * Make sure that if there is a core dump in progress
 723                  * for the old mm, we get out and die instead of going
 724                  * through with the exec.  We must hold mmap_sem around
 725                  * checking core_state and changing tsk->mm.
 726                  */
 727                 down_read(&old_mm->mmap_sem);
 728                 if (unlikely(old_mm->core_state)) {
 729                         up_read(&old_mm->mmap_sem);
 730                         return -EINTR;
 731                 }
 732         }
 733         task_lock(tsk);
 734         active_mm = tsk->active_mm;
 735         tsk->mm = mm;
 736         tsk->active_mm = mm;
 737         activate_mm(active_mm, mm);
 738         task_unlock(tsk);
 739         mm_update_next_owner(old_mm);
 740         arch_pick_mmap_layout(mm);
 741         if (old_mm) {
 742                 up_read(&old_mm->mmap_sem);
 743                 BUG_ON(active_mm != old_mm);
 744                 mmput(old_mm);
 745                 return 0;
 746         }
 747         mmdrop(active_mm);
 748         return 0;
 749 }
 750
 751 /*
 752  * This function makes sure the current process has its own signal table,
 753  * so that flush_signal_handlers can later reset the handlers without
 754  * disturbing other processes.  (Other processes might share the signal
 755  * table via the CLONE_SIGHAND option to clone().)
 756  */
 757 static int de_thread(struct task_struct *tsk)
 758 {
 759         struct signal_struct *sig = tsk->signal;
 760         struct sighand_struct *oldsighand = tsk->sighand;
 761         spinlock_t *lock = &oldsighand->siglock;
 762         struct task_struct *leader = NULL;
 763         int count;
 764
 765         if (thread_group_empty(tsk))
 766                 goto no_thread_group;
 767
 768         /*
 769          * Kill all other threads in the thread group.
 770          */
 771         spin_lock_irq(lock);
 772         if (signal_group_exit(sig)) {
 773                 /*
 774                  * Another group action in progress, just
 775                  * return so that the signal is processed.
 776                  */
 777                 spin_unlock_irq(lock);
 778                 return -EAGAIN;
 779         }
 780         sig->group_exit_task = tsk;
 781         zap_other_threads(tsk);
 782
 783         /* Account for the thread group leader hanging around: */
 784         count = thread_group_leader(tsk) ? 1 : 2;
 785         sig->notify_count = count;
 786         while (atomic_read(&sig->count) > count) {
 787                 __set_current_state(TASK_UNINTERRUPTIBLE);
 788                 spin_unlock_irq(lock);
 789                 schedule();
 790                 spin_lock_irq(lock);
 791         }
 792         spin_unlock_irq(lock);
 793
 794         /*
 795          * At this point all other threads have exited, all we have to
 796          * do is to wait for the thread group leader to become inactive,
 797          * and to assume its PID:
 798          */
 799         if (!thread_group_leader(tsk)) {
 800                 leader = tsk->group_leader;
 801
 802                 sig->notify_count = -1; /* for exit_notify() */
 803                 for (;;) {
 804                         write_lock_irq(&tasklist_lock);
 805                         if (likely(leader->exit_state))
 806                                 break;
 807                         __set_current_state(TASK_UNINTERRUPTIBLE);
 808                         write_unlock_irq(&tasklist_lock);
 809                         schedule();
 810                 }
 811
 812                 if (unlikely(task_child_reaper(tsk) == leader))
 813                         task_active_pid_ns(tsk)->child_reaper = tsk;
 814                 /*
 815                  * The only record we have of the real-time age of a
 816                  * process, regardless of execs it's done, is start_time.
 817                  * All the past CPU time is accumulated in signal_struct
 818                  * from sister threads now dead.  But in this non-leader
 819                  * exec, nothing survives from the original leader thread,
 820                  * whose birth marks the true age of this process now.
 821                  * When we take on its identity by switching to its PID, we
 822                  * also take its birthdate (always earlier than our own).
 823                  */
 824                 tsk->start_time = leader->start_time;
 825
 826                 BUG_ON(!same_thread_group(leader, tsk));
 827                 BUG_ON(has_group_leader_pid(tsk));
 828                 /*
 829                  * An exec() starts a new thread group with the
 830                  * TGID of the previous thread group. Rehash the
 831                  * two threads with a switched PID, and release
 832                  * the former thread group leader:
 833                  */
 834
 835                 /* Become a process group leader with the old leader's pid.
 836                  * The old leader becomes a thread of the this thread group.
 837                  * Note: The old leader also uses this pid until release_task
 838                  *       is called.  Odd but simple and correct.
 839                  */
 840                 detach_pid(tsk, PIDTYPE_PID);
 841                 tsk->pid = leader->pid;
 842                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 843                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 844                 transfer_pid(leader, tsk, PIDTYPE_SID);
 845                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 846
 847                 tsk->group_leader = tsk;
 848                 leader->group_leader = tsk;
 849
 850                 tsk->exit_signal = SIGCHLD;
 851
 852                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 853                 leader->exit_state = EXIT_DEAD;
 854
 855                 write_unlock_irq(&tasklist_lock);
 856         }
 857
 858         sig->group_exit_task = NULL;
 859         sig->notify_count = 0;
 860
 861 no_thread_group:
 862         exit_itimers(sig);
 863         flush_itimer_signals();
 864         if (leader)
 865                 release_task(leader);
 866
 867         if (atomic_read(&oldsighand->count) != 1) {
 868                 struct sighand_struct *newsighand;
 869                 /*
 870                  * This ->sighand is shared with the CLONE_SIGHAND
 871                  * but not CLONE_THREAD task, switch to the new one.
 872                  */
 873                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 874                 if (!newsighand)
 875                         return -ENOMEM;
 876
 877                 atomic_set(&newsighand->count, 1);
 878                 memcpy(newsighand->action, oldsighand->action,
 879                        sizeof(newsighand->action));
 880
 881                 write_lock_irq(&tasklist_lock);
 882                 spin_lock(&oldsighand->siglock);
 883                 rcu_assign_pointer(tsk->sighand, newsighand);
 884                 spin_unlock(&oldsighand->siglock);
 885                 write_unlock_irq(&tasklist_lock);
 886
 887                 __cleanup_sighand(oldsighand);
 888         }
 889
 890         BUG_ON(!thread_group_leader(tsk));
 891         return 0;
 892 }
 893
 894 /*
 895  * These functions flushes out all traces of the currently running executable
 896  * so that a new one can be started
 897  */
 898 static void flush_old_files(struct files_struct * files)
 899 {
 900         long j = -1;
 901         struct fdtable *fdt;
 902
 903         spin_lock(&files->file_lock);
 904         for (;;) {
 905                 unsigned long set, i;
 906
 907                 j++;
 908                 i = j * __NFDBITS;
 909                 fdt = files_fdtable(files);
 910                 if (i >= fdt->max_fds)
 911                         break;
 912                 set = fdt->close_on_exec->fds_bits[j];
 913                 if (!set)
 914                         continue;
 915                 fdt->close_on_exec->fds_bits[j] = 0;
 916                 spin_unlock(&files->file_lock);
 917                 for ( ; set ; i++,set >>= 1) {
 918                         if (set & 1) {
 919                                 sys_close(i);
 920                         }
 921                 }
 922                 spin_lock(&files->file_lock);
 923
 924         }
 925         spin_unlock(&files->file_lock);
 926 }
 927
 928 char *get_task_comm(char *buf, struct task_struct *tsk)
 929 {
 930         /* buf must be at least sizeof(tsk->comm) in size */
 931         task_lock(tsk);
 932         strncpy(buf, tsk->comm, sizeof(tsk->comm));
 933         task_unlock(tsk);
 934         return buf;
 935 }
 936
 937 void set_task_comm(struct task_struct *tsk, char *buf)
 938 {
 939         task_lock(tsk);
 940         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 941         task_unlock(tsk);
 942 }
 943
 944 int flush_old_exec(struct linux_binprm * bprm)
 945 {
 946         char * name;
 947         int i, ch, retval;
 948         char tcomm[sizeof(current->comm)];
 949
 950         /*
 951          * Make sure we have a private signal table and that
 952          * we are unassociated from the previous thread group.
 953          */
 954         retval = de_thread(current);
 955         if (retval)
 956                 goto out;
 957
 958         set_mm_exe_file(bprm->mm, bprm->file);
 959
 960         /*
 961          * Release all of the old mmap stuff
 962          */
 963         retval = exec_mmap(bprm->mm);
 964         if (retval)
 965                 goto out;
 966
 967         bprm->mm = NULL;                /* We're using it now */
 968
 969         /* This is the point of no return */
 970         current->sas_ss_sp = current->sas_ss_size = 0;
 971
 972         if (current->euid == current->uid && current->egid == current->gid)
 973                 set_dumpable(current->mm, 1);
 974         else
 975                 set_dumpable(current->mm, suid_dumpable);
 976
 977         name = bprm->filename;
 978
 979         /* Copies the binary name from after last slash */
 980         for (i=0; (ch = *(name++)) != '\0';) {
 981                 if (ch == '/')
 982                         i = 0; /* overwrite what we wrote */
 983                 else
 984                         if (i < (sizeof(tcomm) - 1))
 985                                 tcomm[i++] = ch;
 986         }
 987         tcomm[i] = '\0';
 988         set_task_comm(current, tcomm);
 989
 990         current->flags &= ~PF_RANDOMIZE;
 991         flush_thread();
 992
 993         /* Set the new mm task size. We have to do that late because it may
 994          * depend on TIF_32BIT which is only updated in flush_thread() on
 995          * some architectures like powerpc
 996          */
 997         current->mm->task_size = TASK_SIZE;
 998
 999         if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) {
1000                 suid_keys(current);
1001                 set_dumpable(current->mm, suid_dumpable);
1002                 current->pdeath_signal = 0;
1003         } else if (file_permission(bprm->file, MAY_READ) ||
1004                         (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
1005                 suid_keys(current);
1006                 set_dumpable(current->mm, suid_dumpable);
1007         }
1008
1009         /* An exec changes our domain. We are no longer part of the thread
1010            group */
1011
1012         current->self_exec_id++;
1013
1014         flush_signal_handlers(current, 0);
1015         flush_old_files(current->files);
1016
1017         return 0;
1018
1019 out:
1020         return retval;
1021 }
1022
1023 EXPORT_SYMBOL(flush_old_exec);
1024
1025 /*
1026  * Fill the binprm structure from the inode.
1027  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1028  */
1029 int prepare_binprm(struct linux_binprm *bprm)
1030 {
1031         int mode;
1032         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1033         int retval;
1034
1035         mode = inode->i_mode;
1036         if (bprm->file->f_op == NULL)
1037                 return -EACCES;
1038
1039         bprm->e_uid = current->euid;
1040         bprm->e_gid = current->egid;
1041
1042         if(!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1043                 /* Set-uid? */
1044                 if (mode & S_ISUID) {
1045                         current->personality &= ~PER_CLEAR_ON_SETID;
1046                         bprm->e_uid = inode->i_uid;
1047                 }
1048
1049                 /* Set-gid? */
1050                 /*
1051                  * If setgid is set but no group execute bit then this
1052                  * is a candidate for mandatory locking, not a setgid
1053                  * executable.
1054                  */
1055                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1056                         current->personality &= ~PER_CLEAR_ON_SETID;
1057                         bprm->e_gid = inode->i_gid;
1058                 }
1059         }
1060
1061         /* fill in binprm security blob */
1062         retval = security_bprm_set(bprm);
1063         if (retval)
1064                 return retval;
1065
1066         memset(bprm->buf,0,BINPRM_BUF_SIZE);
1067         return kernel_read(bprm->file,0,bprm->buf,BINPRM_BUF_SIZE);
1068 }
1069
1070 EXPORT_SYMBOL(prepare_binprm);
1071
1072 static int unsafe_exec(struct task_struct *p)
1073 {
1074         int unsafe = 0;
1075         if (p->ptrace & PT_PTRACED) {
1076                 if (p->ptrace & PT_PTRACE_CAP)
1077                         unsafe |= LSM_UNSAFE_PTRACE_CAP;
1078                 else
1079                         unsafe |= LSM_UNSAFE_PTRACE;
1080         }
1081         if (atomic_read(&p->fs->count) > 1 ||
1082             atomic_read(&p->files->count) > 1 ||
1083             atomic_read(&p->sighand->count) > 1)
1084                 unsafe |= LSM_UNSAFE_SHARE;
1085
1086         return unsafe;
1087 }
1088
1089 void compute_creds(struct linux_binprm *bprm)
1090 {
1091         int unsafe;
1092
1093         if (bprm->e_uid != current->uid) {
1094                 suid_keys(current);
1095                 current->pdeath_signal = 0;
1096         }
1097         exec_keys(current);
1098
1099         task_lock(current);
1100         unsafe = unsafe_exec(current);
1101         security_bprm_apply_creds(bprm, unsafe);
1102         task_unlock(current);
1103         security_bprm_post_apply_creds(bprm);
1104 }
1105 EXPORT_SYMBOL(compute_creds);
1106
1107 /*
1108  * Arguments are '\0' separated strings found at the location bprm->p
1109  * points to; chop off the first by relocating brpm->p to right after
1110  * the first '\0' encountered.
1111  */
1112 int remove_arg_zero(struct linux_binprm *bprm)
1113 {
1114         int ret = 0;
1115         unsigned long offset;
1116         char *kaddr;
1117         struct page *page;
1118
1119         if (!bprm->argc)
1120                 return 0;
1121
1122         do {
1123                 offset = bprm->p & ~PAGE_MASK;
1124                 page = get_arg_page(bprm, bprm->p, 0);
1125                 if (!page) {
1126                         ret = -EFAULT;
1127                         goto out;
1128                 }
1129                 kaddr = kmap_atomic(page, KM_USER0);
1130
1131                 for (; offset < PAGE_SIZE && kaddr[offset];
1132                                 offset++, bprm->p++)
1133                         ;
1134
1135                 kunmap_atomic(kaddr, KM_USER0);
1136                 put_arg_page(page);
1137
1138                 if (offset == PAGE_SIZE)
1139                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1140         } while (offset == PAGE_SIZE);
1141
1142         bprm->p++;
1143         bprm->argc--;
1144         ret = 0;
1145
1146 out:
1147         return ret;
1148 }
1149 EXPORT_SYMBOL(remove_arg_zero);
1150
1151 /*
1152  * cycle the list of binary formats handler, until one recognizes the image
1153  */
1154 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1155 {
1156         int try,retval;
1157         struct linux_binfmt *fmt;
1158 #ifdef __alpha__
1159         /* handle /sbin/loader.. */
1160         {
1161             struct exec * eh = (struct exec *) bprm->buf;
1162
1163             if (!bprm->loader && eh->fh.f_magic == 0x183 &&
1164                 (eh->fh.f_flags & 0x3000) == 0x3000)
1165             {
1166                 struct file * file;
1167                 unsigned long loader;
1168
1169                 allow_write_access(bprm->file);
1170                 fput(bprm->file);
1171                 bprm->file = NULL;
1172
1173                 loader = bprm->vma->vm_end - sizeof(void *);
1174
1175                 file = open_exec("/sbin/loader");
1176                 retval = PTR_ERR(file);
1177                 if (IS_ERR(file))
1178                         return retval;
1179
1180                 /* Remember if the application is TASO.  */
1181                 bprm->sh_bang = eh->ah.entry < 0x100000000UL;
1182
1183                 bprm->file = file;
1184                 bprm->loader = loader;
1185                 retval = prepare_binprm(bprm);
1186                 if (retval<0)
1187                         return retval;
1188                 /* should call search_binary_handler recursively here,
1189                    but it does not matter */
1190             }
1191         }
1192 #endif
1193         retval = security_bprm_check(bprm);
1194         if (retval)
1195                 return retval;
1196
1197         /* kernel module loader fixup */
1198         /* so we don't try to load run modprobe in kernel space. */
1199         set_fs(USER_DS);
1200
1201         retval = audit_bprm(bprm);
1202         if (retval)
1203                 return retval;
1204
1205         retval = -ENOENT;
1206         for (try=0; try<2; try++) {
1207                 read_lock(&binfmt_lock);
1208                 list_for_each_entry(fmt, &formats, lh) {
1209                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1210                         if (!fn)
1211                                 continue;
1212                         if (!try_module_get(fmt->module))
1213                                 continue;
1214                         read_unlock(&binfmt_lock);
1215                         retval = fn(bprm, regs);
1216                         if (retval >= 0) {
1217                                 put_binfmt(fmt);
1218                                 allow_write_access(bprm->file);
1219                                 if (bprm->file)
1220                                         fput(bprm->file);
1221                                 bprm->file = NULL;
1222                                 current->did_exec = 1;
1223                                 proc_exec_connector(current);
1224                                 return retval;
1225                         }
1226                         read_lock(&binfmt_lock);
1227                         put_binfmt(fmt);
1228                         if (retval != -ENOEXEC || bprm->mm == NULL)
1229                                 break;
1230                         if (!bprm->file) {
1231                                 read_unlock(&binfmt_lock);
1232                                 return retval;
1233                         }
1234                 }
1235                 read_unlock(&binfmt_lock);
1236                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1237                         break;
1238 #ifdef CONFIG_KMOD
1239                 }else{
1240 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1241                         if (printable(bprm->buf[0]) &&
1242                             printable(bprm->buf[1]) &&
1243                             printable(bprm->buf[2]) &&
1244                             printable(bprm->buf[3]))
1245                                 break; /* -ENOEXEC */
1246                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1247 #endif
1248                 }
1249         }
1250         return retval;
1251 }
1252
1253 EXPORT_SYMBOL(search_binary_handler);
1254
1255 void free_bprm(struct linux_binprm *bprm)
1256 {
1257         free_arg_pages(bprm);
1258         kfree(bprm);
1259 }
1260
1261 /*
1262  * sys_execve() executes a new program.
1263  */
1264 int do_execve(char * filename,
1265         char __user *__user *argv,
1266         char __user *__user *envp,
1267         struct pt_regs * regs)
1268 {
1269         struct linux_binprm *bprm;
1270         struct file *file;
1271         struct files_struct *displaced;
1272         int retval;
1273
1274         retval = unshare_files(&displaced);
1275         if (retval)
1276                 goto out_ret;
1277
1278         retval = -ENOMEM;
1279         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1280         if (!bprm)
1281                 goto out_files;
1282
1283         file = open_exec(filename);
1284         retval = PTR_ERR(file);
1285         if (IS_ERR(file))
1286                 goto out_kfree;
1287
1288         sched_exec();
1289
1290         bprm->file = file;
1291         bprm->filename = filename;
1292         bprm->interp = filename;
1293
1294         retval = bprm_mm_init(bprm);
1295         if (retval)
1296                 goto out_file;
1297
1298         bprm->argc = count(argv, MAX_ARG_STRINGS);
1299         if ((retval = bprm->argc) < 0)
1300                 goto out_mm;
1301
1302         bprm->envc = count(envp, MAX_ARG_STRINGS);
1303         if ((retval = bprm->envc) < 0)
1304                 goto out_mm;
1305
1306         retval = security_bprm_alloc(bprm);
1307         if (retval)
1308                 goto out;
1309
1310         retval = prepare_binprm(bprm);
1311         if (retval < 0)
1312                 goto out;
1313
1314         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1315         if (retval < 0)
1316                 goto out;
1317
1318         bprm->exec = bprm->p;
1319         retval = copy_strings(bprm->envc, envp, bprm);
1320         if (retval < 0)
1321                 goto out;
1322
1323         retval = copy_strings(bprm->argc, argv, bprm);
1324         if (retval < 0)
1325                 goto out;
1326
1327         current->flags &= ~PF_KTHREAD;
1328         retval = search_binary_handler(bprm,regs);
1329         if (retval >= 0) {
1330                 /* execve success */
1331                 security_bprm_free(bprm);
1332                 acct_update_integrals(current);
1333                 free_bprm(bprm);
1334                 if (displaced)
1335                         put_files_struct(displaced);
1336                 return retval;
1337         }
1338
1339 out:
1340         if (bprm->security)
1341                 security_bprm_free(bprm);
1342
1343 out_mm:
1344         if (bprm->mm)
1345                 mmput (bprm->mm);
1346
1347 out_file:
1348         if (bprm->file) {
1349                 allow_write_access(bprm->file);
1350                 fput(bprm->file);
1351         }
1352 out_kfree:
1353         free_bprm(bprm);
1354
1355 out_files:
1356         if (displaced)
1357                 reset_files_struct(displaced);
1358 out_ret:
1359         return retval;
1360 }
1361
1362 int set_binfmt(struct linux_binfmt *new)
1363 {
1364         struct linux_binfmt *old = current->binfmt;
1365
1366         if (new) {
1367                 if (!try_module_get(new->module))
1368                         return -1;
1369         }
1370         current->binfmt = new;
1371         if (old)
1372                 module_put(old->module);
1373         return 0;
1374 }
1375
1376 EXPORT_SYMBOL(set_binfmt);
1377
1378 /* format_corename will inspect the pattern parameter, and output a
1379  * name into corename, which must have space for at least
1380  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1381  */
1382 static int format_corename(char *corename, const char *pattern, long signr)
1383 {
1384         const char *pat_ptr = pattern;
1385         char *out_ptr = corename;
1386         char *const out_end = corename + CORENAME_MAX_SIZE;
1387         int rc;
1388         int pid_in_pattern = 0;
1389         int ispipe = 0;
1390
1391         if (*pattern == '|')
1392                 ispipe = 1;
1393
1394         /* Repeat as long as we have more pattern to process and more output
1395            space */
1396         while (*pat_ptr) {
1397                 if (*pat_ptr != '%') {
1398                         if (out_ptr == out_end)
1399                                 goto out;
1400                         *out_ptr++ = *pat_ptr++;
1401                 } else {
1402                         switch (*++pat_ptr) {
1403                         case 0:
1404                                 goto out;
1405                         /* Double percent, output one percent */
1406                         case '%':
1407                                 if (out_ptr == out_end)
1408                                         goto out;
1409                                 *out_ptr++ = '%';
1410                                 break;
1411                         /* pid */
1412                         case 'p':
1413                                 pid_in_pattern = 1;
1414                                 rc = snprintf(out_ptr, out_end - out_ptr,
1415                                               "%d", task_tgid_vnr(current));
1416                                 if (rc > out_end - out_ptr)
1417                                         goto out;
1418                                 out_ptr += rc;
1419                                 break;
1420                         /* uid */
1421                         case 'u':
1422                                 rc = snprintf(out_ptr, out_end - out_ptr,
1423                                               "%d", current->uid);
1424                                 if (rc > out_end - out_ptr)
1425                                         goto out;
1426                                 out_ptr += rc;
1427                                 break;
1428                         /* gid */
1429                         case 'g':
1430                                 rc = snprintf(out_ptr, out_end - out_ptr,
1431                                               "%d", current->gid);
1432                                 if (rc > out_end - out_ptr)
1433                                         goto out;
1434                                 out_ptr += rc;
1435                                 break;
1436                         /* signal that caused the coredump */
1437                         case 's':
1438                                 rc = snprintf(out_ptr, out_end - out_ptr,
1439                                               "%ld", signr);
1440                                 if (rc > out_end - out_ptr)
1441                                         goto out;
1442                                 out_ptr += rc;
1443                                 break;
1444                         /* UNIX time of coredump */
1445                         case 't': {
1446                                 struct timeval tv;
1447                                 do_gettimeofday(&tv);
1448                                 rc = snprintf(out_ptr, out_end - out_ptr,
1449                                               "%lu", tv.tv_sec);
1450                                 if (rc > out_end - out_ptr)
1451                                         goto out;
1452                                 out_ptr += rc;
1453                                 break;
1454                         }
1455                         /* hostname */
1456                         case 'h':
1457                                 down_read(&uts_sem);
1458                                 rc = snprintf(out_ptr, out_end - out_ptr,
1459                                               "%s", utsname()->nodename);
1460                                 up_read(&uts_sem);
1461                                 if (rc > out_end - out_ptr)
1462                                         goto out;
1463                                 out_ptr += rc;
1464                                 break;
1465                         /* executable */
1466                         case 'e':
1467                                 rc = snprintf(out_ptr, out_end - out_ptr,
1468                                               "%s", current->comm);
1469                                 if (rc > out_end - out_ptr)
1470                                         goto out;
1471                                 out_ptr += rc;
1472                                 break;
1473                         /* core limit size */
1474                         case 'c':
1475                                 rc = snprintf(out_ptr, out_end - out_ptr,
1476                                               "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1477                                 if (rc > out_end - out_ptr)
1478                                         goto out;
1479                                 out_ptr += rc;
1480                                 break;
1481                         default:
1482                                 break;
1483                         }
1484                         ++pat_ptr;
1485                 }
1486         }
1487         /* Backward compatibility with core_uses_pid:
1488          *
1489          * If core_pattern does not include a %p (as is the default)
1490          * and core_uses_pid is set, then .%pid will be appended to
1491          * the filename. Do not do this for piped commands. */
1492         if (!ispipe && !pid_in_pattern
1493             && (core_uses_pid || atomic_read(&current->mm->mm_users) != 1)) {
1494                 rc = snprintf(out_ptr, out_end - out_ptr,
1495                               ".%d", task_tgid_vnr(current));
1496                 if (rc > out_end - out_ptr)
1497                         goto out;
1498                 out_ptr += rc;
1499         }
1500 out:
1501         *out_ptr = 0;
1502         return ispipe;
1503 }
1504
1505 static int zap_process(struct task_struct *start)
1506 {
1507         struct task_struct *t;
1508         int nr = 0;
1509
1510         start->signal->flags = SIGNAL_GROUP_EXIT;
1511         start->signal->group_stop_count = 0;
1512
1513         t = start;
1514         do {
1515                 if (t != current && t->mm) {
1516                         sigaddset(&t->pending.signal, SIGKILL);
1517                         signal_wake_up(t, 1);
1518                         nr++;
1519                 }
1520         } while_each_thread(start, t);
1521
1522         return nr;
1523 }
1524
1525 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1526                                 struct core_state *core_state, int exit_code)
1527 {
1528         struct task_struct *g, *p;
1529         unsigned long flags;
1530         int nr = -EAGAIN;
1531
1532         spin_lock_irq(&tsk->sighand->siglock);
1533         if (!signal_group_exit(tsk->signal)) {
1534                 mm->core_state = core_state;
1535                 tsk->signal->group_exit_code = exit_code;
1536                 nr = zap_process(tsk);
1537         }
1538         spin_unlock_irq(&tsk->sighand->siglock);
1539         if (unlikely(nr < 0))
1540                 return nr;
1541
1542         if (atomic_read(&mm->mm_users) == nr + 1)
1543                 goto done;
1544         /*
1545          * We should find and kill all tasks which use this mm, and we should
1546          * count them correctly into ->nr_threads. We don't take tasklist
1547          * lock, but this is safe wrt:
1548          *
1549          * fork:
1550          *      None of sub-threads can fork after zap_process(leader). All
1551          *      processes which were created before this point should be
1552          *      visible to zap_threads() because copy_process() adds the new
1553          *      process to the tail of init_task.tasks list, and lock/unlock
1554          *      of ->siglock provides a memory barrier.
1555          *
1556          * do_exit:
1557          *      The caller holds mm->mmap_sem. This means that the task which
1558          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1559          *      its ->mm.
1560          *
1561          * de_thread:
1562          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1563          *      we must see either old or new leader, this does not matter.
1564          *      However, it can change p->sighand, so lock_task_sighand(p)
1565          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1566          *      it can't fail.
1567          *
1568          *      Note also that "g" can be the old leader with ->mm == NULL
1569          *      and already unhashed and thus removed from ->thread_group.
1570          *      This is OK, __unhash_process()->list_del_rcu() does not
1571          *      clear the ->next pointer, we will find the new leader via
1572          *      next_thread().
1573          */
1574         rcu_read_lock();
1575         for_each_process(g) {
1576                 if (g == tsk->group_leader)
1577                         continue;
1578                 if (g->flags & PF_KTHREAD)
1579                         continue;
1580                 p = g;
1581                 do {
1582                         if (p->mm) {
1583                                 if (unlikely(p->mm == mm)) {
1584                                         lock_task_sighand(p, &flags);
1585                                         nr += zap_process(p);
1586                                         unlock_task_sighand(p, &flags);
1587                                 }
1588                                 break;
1589                         }
1590                 } while_each_thread(g, p);
1591         }
1592         rcu_read_unlock();
1593 done:
1594         core_state->nr_threads = nr;
1595         return nr;
1596 }
1597
1598 static int coredump_wait(int exit_code)
1599 {
1600         struct task_struct *tsk = current;
1601         struct mm_struct *mm = tsk->mm;
1602         struct core_state core_state;
1603         struct completion *vfork_done;
1604         int core_waiters;
1605
1606         init_completion(&mm->core_done);
1607         init_completion(&core_state.startup);
1608         core_waiters = zap_threads(tsk, mm, &core_state, exit_code);
1609         up_write(&mm->mmap_sem);
1610
1611         if (unlikely(core_waiters < 0))
1612                 goto fail;
1613
1614         /*
1615          * Make sure nobody is waiting for us to release the VM,
1616          * otherwise we can deadlock when we wait on each other
1617          */
1618         vfork_done = tsk->vfork_done;
1619         if (vfork_done) {
1620                 tsk->vfork_done = NULL;
1621                 complete(vfork_done);
1622         }
1623
1624         if (core_waiters)
1625                 wait_for_completion(&core_state.startup);
1626         mm->core_state = NULL;
1627 fail:
1628         return core_waiters;
1629 }
1630
1631 /*
1632  * set_dumpable converts traditional three-value dumpable to two flags and
1633  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1634  * these bits are not changed atomically.  So get_dumpable can observe the
1635  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1636  * return either old dumpable or new one by paying attention to the order of
1637  * modifying the bits.
1638  *
1639  * dumpable |   mm->flags (binary)
1640  * old  new | initial interim  final
1641  * ---------+-----------------------
1642  *  0    1  |   00      01      01
1643  *  0    2  |   00      10(*)   11
1644  *  1    0  |   01      00      00
1645  *  1    2  |   01      11      11
1646  *  2    0  |   11      10(*)   00
1647  *  2    1  |   11      11      01
1648  *
1649  * (*) get_dumpable regards interim value of 10 as 11.
1650  */
1651 void set_dumpable(struct mm_struct *mm, int value)
1652 {
1653         switch (value) {
1654         case 0:
1655                 clear_bit(MMF_DUMPABLE, &mm->flags);
1656                 smp_wmb();
1657                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1658                 break;
1659         case 1:
1660                 set_bit(MMF_DUMPABLE, &mm->flags);
1661                 smp_wmb();
1662                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1663                 break;
1664         case 2:
1665                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1666                 smp_wmb();
1667                 set_bit(MMF_DUMPABLE, &mm->flags);
1668                 break;
1669         }
1670 }
1671
1672 int get_dumpable(struct mm_struct *mm)
1673 {
1674         int ret;
1675
1676         ret = mm->flags & 0x3;
1677         return (ret >= 2) ? 2 : ret;
1678 }
1679
1680 int do_coredump(long signr, int exit_code, struct pt_regs * regs)
1681 {
1682         char corename[CORENAME_MAX_SIZE + 1];
1683         struct mm_struct *mm = current->mm;
1684         struct linux_binfmt * binfmt;
1685         struct inode * inode;
1686         struct file * file;
1687         int retval = 0;
1688         int fsuid = current->fsuid;
1689         int flag = 0;
1690         int ispipe = 0;
1691         unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1692         char **helper_argv = NULL;
1693         int helper_argc = 0;
1694         char *delimit;
1695
1696         audit_core_dumps(signr);
1697
1698         binfmt = current->binfmt;
1699         if (!binfmt || !binfmt->core_dump)
1700                 goto fail;
1701         down_write(&mm->mmap_sem);
1702         /*
1703          * If another thread got here first, or we are not dumpable, bail out.
1704          */
1705         if (mm->core_state || !get_dumpable(mm)) {
1706                 up_write(&mm->mmap_sem);
1707                 goto fail;
1708         }
1709
1710         /*
1711          *      We cannot trust fsuid as being the "true" uid of the
1712          *      process nor do we know its entire history. We only know it
1713          *      was tainted so we dump it as root in mode 2.
1714          */
1715         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1716                 flag = O_EXCL;          /* Stop rewrite attacks */
1717                 current->fsuid = 0;     /* Dump root private */
1718         }
1719
1720         retval = coredump_wait(exit_code);
1721         if (retval < 0)
1722                 goto fail;
1723
1724         /*
1725          * Clear any false indication of pending signals that might
1726          * be seen by the filesystem code called to write the core file.
1727          */
1728         clear_thread_flag(TIF_SIGPENDING);
1729
1730         /*
1731          * lock_kernel() because format_corename() is controlled by sysctl, which
1732          * uses lock_kernel()
1733          */
1734         lock_kernel();
1735         ispipe = format_corename(corename, core_pattern, signr);
1736         unlock_kernel();
1737         /*
1738          * Don't bother to check the RLIMIT_CORE value if core_pattern points
1739          * to a pipe.  Since we're not writing directly to the filesystem
1740          * RLIMIT_CORE doesn't really apply, as no actual core file will be
1741          * created unless the pipe reader choses to write out the core file
1742          * at which point file size limits and permissions will be imposed
1743          * as it does with any other process
1744          */
1745         if ((!ispipe) && (core_limit < binfmt->min_coredump))
1746                 goto fail_unlock;
1747
1748         if (ispipe) {
1749                 helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1750                 /* Terminate the string before the first option */
1751                 delimit = strchr(corename, ' ');
1752                 if (delimit)
1753                         *delimit = '\0';
1754                 delimit = strrchr(helper_argv[0], '/');
1755                 if (delimit)
1756                         delimit++;
1757                 else
1758                         delimit = helper_argv[0];
1759                 if (!strcmp(delimit, current->comm)) {
1760                         printk(KERN_NOTICE "Recursive core dump detected, "
1761                                         "aborting\n");
1762                         goto fail_unlock;
1763                 }
1764
1765                 core_limit = RLIM_INFINITY;
1766
1767                 /* SIGPIPE can happen, but it's just never processed */
1768                 if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
1769                                 &file)) {
1770                         printk(KERN_INFO "Core dump to %s pipe failed\n",
1771                                corename);
1772                         goto fail_unlock;
1773                 }
1774         } else
1775                 file = filp_open(corename,
1776                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1777                                  0600);
1778         if (IS_ERR(file))
1779                 goto fail_unlock;
1780         inode = file->f_path.dentry->d_inode;
1781         if (inode->i_nlink > 1)
1782                 goto close_fail;        /* multiple links - don't dump */
1783         if (!ispipe && d_unhashed(file->f_path.dentry))
1784                 goto close_fail;
1785
1786         /* AK: actually i see no reason to not allow this for named pipes etc.,
1787            but keep the previous behaviour for now. */
1788         if (!ispipe && !S_ISREG(inode->i_mode))
1789                 goto close_fail;
1790         /*
1791          * Dont allow local users get cute and trick others to coredump
1792          * into their pre-created files:
1793          */
1794         if (inode->i_uid != current->fsuid)
1795                 goto close_fail;
1796         if (!file->f_op)
1797                 goto close_fail;
1798         if (!file->f_op->write)
1799                 goto close_fail;
1800         if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1801                 goto close_fail;
1802
1803         retval = binfmt->core_dump(signr, regs, file, core_limit);
1804
1805         if (retval)
1806                 current->signal->group_exit_code |= 0x80;
1807 close_fail:
1808         filp_close(file, NULL);
1809 fail_unlock:
1810         if (helper_argv)
1811                 argv_free(helper_argv);
1812
1813         current->fsuid = fsuid;
1814         complete_all(&mm->core_done);
1815 fail:
1816         return retval;
1817 }