X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fsignal.c;h=ef8156a6aad519014c030f62e856302dacf045e7;hb=c51aea80a9fbb423b49d432e89e515257bb2b983;hp=bc972d7e6319729b832fd1bde49b70f49549ec58;hpb=7dfb71030f7636a0d65200158113c37764552f93;p=safe%2Fjmp%2Flinux-2.6 diff --git a/kernel/signal.c b/kernel/signal.c index bc972d7..ef8156a 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -12,7 +12,6 @@ #include #include -#include #include #include #include @@ -22,8 +21,12 @@ #include #include #include +#include #include #include +#include +#include + #include #include #include @@ -36,125 +39,6 @@ static struct kmem_cache *sigqueue_cachep; -/* - * In POSIX a signal is sent either to a specific thread (Linux task) - * or to the process as a whole (Linux thread group). How the signal - * is sent determines whether it's to one thread or the whole group, - * which determines which signal mask(s) are involved in blocking it - * from being delivered until later. When the signal is delivered, - * either it's caught or ignored by a user handler or it has a default - * effect that applies to the whole thread group (POSIX process). - * - * The possible effects an unblocked signal set to SIG_DFL can have are: - * ignore - Nothing Happens - * terminate - kill the process, i.e. all threads in the group, - * similar to exit_group. The group leader (only) reports - * WIFSIGNALED status to its parent. - * coredump - write a core dump file describing all threads using - * the same mm and then kill all those threads - * stop - stop all the threads in the group, i.e. TASK_STOPPED state - * - * SIGKILL and SIGSTOP cannot be caught, blocked, or ignored. - * Other signals when not blocked and set to SIG_DFL behaves as follows. - * The job control signals also have other special effects. - * - * +--------------------+------------------+ - * | POSIX signal | default action | - * +--------------------+------------------+ - * | SIGHUP | terminate | - * | SIGINT | terminate | - * | SIGQUIT | coredump | - * | SIGILL | coredump | - * | SIGTRAP | coredump | - * | SIGABRT/SIGIOT | coredump | - * | SIGBUS | coredump | - * | SIGFPE | coredump | - * | SIGKILL | terminate(+) | - * | SIGUSR1 | terminate | - * | SIGSEGV | coredump | - * | SIGUSR2 | terminate | - * | SIGPIPE | terminate | - * | SIGALRM | terminate | - * | SIGTERM | terminate | - * | SIGCHLD | ignore | - * | SIGCONT | ignore(*) | - * | SIGSTOP | stop(*)(+) | - * | SIGTSTP | stop(*) | - * | SIGTTIN | stop(*) | - * | SIGTTOU | stop(*) | - * | SIGURG | ignore | - * | SIGXCPU | coredump | - * | SIGXFSZ | coredump | - * | SIGVTALRM | terminate | - * | SIGPROF | terminate | - * | SIGPOLL/SIGIO | terminate | - * | SIGSYS/SIGUNUSED | coredump | - * | SIGSTKFLT | terminate | - * | SIGWINCH | ignore | - * | SIGPWR | terminate | - * | SIGRTMIN-SIGRTMAX | terminate | - * +--------------------+------------------+ - * | non-POSIX signal | default action | - * +--------------------+------------------+ - * | SIGEMT | coredump | - * +--------------------+------------------+ - * - * (+) For SIGKILL and SIGSTOP the action is "always", not just "default". - * (*) Special job control effects: - * When SIGCONT is sent, it resumes the process (all threads in the group) - * from TASK_STOPPED state and also clears any pending/queued stop signals - * (any of those marked with "stop(*)"). This happens regardless of blocking, - * catching, or ignoring SIGCONT. When any stop signal is sent, it clears - * any pending/queued SIGCONT signals; this happens regardless of blocking, - * catching, or ignored the stop signal, though (except for SIGSTOP) the - * default action of stopping the process may happen later or never. - */ - -#ifdef SIGEMT -#define M_SIGEMT M(SIGEMT) -#else -#define M_SIGEMT 0 -#endif - -#if SIGRTMIN > BITS_PER_LONG -#define M(sig) (1ULL << ((sig)-1)) -#else -#define M(sig) (1UL << ((sig)-1)) -#endif -#define T(sig, mask) (M(sig) & (mask)) - -#define SIG_KERNEL_ONLY_MASK (\ - M(SIGKILL) | M(SIGSTOP) ) - -#define SIG_KERNEL_STOP_MASK (\ - M(SIGSTOP) | M(SIGTSTP) | M(SIGTTIN) | M(SIGTTOU) ) - -#define SIG_KERNEL_COREDUMP_MASK (\ - M(SIGQUIT) | M(SIGILL) | M(SIGTRAP) | M(SIGABRT) | \ - M(SIGFPE) | M(SIGSEGV) | M(SIGBUS) | M(SIGSYS) | \ - M(SIGXCPU) | M(SIGXFSZ) | M_SIGEMT ) - -#define SIG_KERNEL_IGNORE_MASK (\ - M(SIGCONT) | M(SIGCHLD) | M(SIGWINCH) | M(SIGURG) ) - -#define sig_kernel_only(sig) \ - (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_ONLY_MASK)) -#define sig_kernel_coredump(sig) \ - (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_COREDUMP_MASK)) -#define sig_kernel_ignore(sig) \ - (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_IGNORE_MASK)) -#define sig_kernel_stop(sig) \ - (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_STOP_MASK)) - -#define sig_needs_tasklist(sig) ((sig) == SIGCONT) - -#define sig_user_defined(t, signr) \ - (((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) && \ - ((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_IGN)) - -#define sig_fatal(t, signr) \ - (!T(signr, SIG_KERNEL_IGNORE_MASK|SIG_KERNEL_STOP_MASK) && \ - (t)->sighand->action[(signr)-1].sa.sa_handler == SIG_DFL) static int sig_ignored(struct task_struct *t, int sig) { @@ -212,26 +96,43 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked) #define PENDING(p,b) has_pending_signals(&(p)->signal, (b)) -fastcall void recalc_sigpending_tsk(struct task_struct *t) +static int recalc_sigpending_tsk(struct task_struct *t) { if (t->signal->group_stop_count > 0 || (freezing(t)) || PENDING(&t->pending, &t->blocked) || - PENDING(&t->signal->shared_pending, &t->blocked)) + PENDING(&t->signal->shared_pending, &t->blocked)) { set_tsk_thread_flag(t, TIF_SIGPENDING); - else - clear_tsk_thread_flag(t, TIF_SIGPENDING); + return 1; + } + /* + * We must never clear the flag in another thread, or in current + * when it's possible the current syscall is returning -ERESTART*. + * So we don't clear it here, and only callers who know they should do. + */ + return 0; +} + +/* + * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up. + * This is superfluous when called on current, the wakeup is a harmless no-op. + */ +void recalc_sigpending_and_wake(struct task_struct *t) +{ + if (recalc_sigpending_tsk(t)) + signal_wake_up(t, 0); } void recalc_sigpending(void) { - recalc_sigpending_tsk(current); + if (!recalc_sigpending_tsk(current)) + clear_thread_flag(TIF_SIGPENDING); + } /* Given the mask, find the first available signal that should be serviced. */ -static int -next_signal(struct sigpending *pending, sigset_t *mask) +int next_signal(struct sigpending *pending, sigset_t *mask) { unsigned long i, *s, *m, x; int sig = 0; @@ -326,6 +227,16 @@ void flush_signals(struct task_struct *t) spin_unlock_irqrestore(&t->sighand->siglock, flags); } +void ignore_signals(struct task_struct *t) +{ + int i; + + for (i = 0; i < _NSIG; ++i) + t->sighand->action[i].sa.sa_handler = SIG_IGN; + + flush_signals(t); +} + /* * Flush all handlers for a task. */ @@ -344,6 +255,16 @@ flush_signal_handlers(struct task_struct *t, int force_default) } } +int unhandled_signal(struct task_struct *tsk, int sig) +{ + if (is_init(tsk)) + return 1; + if (tsk->ptrace & PT_PTRACED) + return 0; + return (tsk->sighand->action[sig-1].sa.sa_handler == SIG_IGN) || + (tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL); +} + /* Notify the system that a driver wants to block all signals for this * process, and wants to be notified if any signals at all were to be @@ -452,27 +373,58 @@ static int __dequeue_signal(struct sigpending *pending, sigset_t *mask, */ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) { - int signr = __dequeue_signal(&tsk->pending, mask, info); - if (!signr) + int signr = 0; + + /* We only dequeue private signals from ourselves, we don't let + * signalfd steal them + */ + if (tsk == current) + signr = __dequeue_signal(&tsk->pending, mask, info); + if (!signr) { signr = __dequeue_signal(&tsk->signal->shared_pending, mask, info); - recalc_sigpending_tsk(tsk); - if (signr && unlikely(sig_kernel_stop(signr))) { - /* - * Set a marker that we have dequeued a stop signal. Our - * caller might release the siglock and then the pending - * stop signal it is about to process is no longer in the - * pending bitmasks, but must still be cleared by a SIGCONT - * (and overruled by a SIGKILL). So those cases clear this - * shared flag after we've set it. Note that this flag may - * remain set after the signal we return is ignored or - * handled. That doesn't matter because its only purpose - * is to alert stop-signal processing code when another - * processor has come along and cleared the flag. - */ - if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) - tsk->signal->flags |= SIGNAL_STOP_DEQUEUED; - } + /* + * itimer signal ? + * + * itimers are process shared and we restart periodic + * itimers in the signal delivery path to prevent DoS + * attacks in the high resolution timer case. This is + * compliant with the old way of self restarting + * itimers, as the SIGALRM is a legacy signal and only + * queued once. Changing the restart behaviour to + * restart the timer in the signal dequeue path is + * reducing the timer noise on heavy loaded !highres + * systems too. + */ + if (unlikely(signr == SIGALRM)) { + struct hrtimer *tmr = &tsk->signal->real_timer; + + if (!hrtimer_is_queued(tmr) && + tsk->signal->it_real_incr.tv64 != 0) { + hrtimer_forward(tmr, tmr->base->get_time(), + tsk->signal->it_real_incr); + hrtimer_restart(tmr); + } + } + } + if (likely(tsk == current)) + recalc_sigpending(); + if (signr && unlikely(sig_kernel_stop(signr))) { + /* + * Set a marker that we have dequeued a stop signal. Our + * caller might release the siglock and then the pending + * stop signal it is about to process is no longer in the + * pending bitmasks, but must still be cleared by a SIGCONT + * (and overruled by a SIGKILL). So those cases clear this + * shared flag after we've set it. Note that this flag may + * remain set after the signal we return is ignored or + * handled. That doesn't matter because its only purpose + * is to alert stop-signal processing code when another + * processor has come along and cleared the flag. + */ + if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) + tsk->signal->flags |= SIGNAL_STOP_DEQUEUED; + } if ( signr && ((info->si_code & __SI_MASK) == __SI_TIMER) && info->si_sys_private){ @@ -580,19 +532,21 @@ static int check_kill_permission(int sig, struct siginfo *info, int error = -EINVAL; if (!valid_signal(sig)) return error; + + error = audit_signal_info(sig, t); /* Let audit system see the signal */ + if (error) + return error; + error = -EPERM; if ((info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) && ((sig != SIGCONT) || - (current->signal->session != t->signal->session)) + (process_session(current) != process_session(t))) && (current->euid ^ t->suid) && (current->euid ^ t->uid) && (current->uid ^ t->suid) && (current->uid ^ t->uid) && !capable(CAP_KILL)) return error; - error = security_task_kill(t, info, sig, 0); - if (!error) - audit_signal_info(sig, t); /* Let audit system see the signal */ - return error; + return security_task_kill(t, info, sig, 0); } /* forward decl */ @@ -713,6 +667,12 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t, int ret = 0; /* + * Deliver the signal to listening signalfds. This must be called + * with the sighand lock held. + */ + signalfd_notify(t, sig); + + /* * fast-pathed signals for kernel-internal things like SIGSTOP * or SIGKILL. */ @@ -768,6 +728,37 @@ out_set: #define LEGACY_QUEUE(sigptr, sig) \ (((sig) < SIGRTMIN) && sigismember(&(sigptr)->signal, (sig))) +int print_fatal_signals; + +static void print_fatal_signal(struct pt_regs *regs, int signr) +{ + printk("%s/%d: potentially unexpected fatal signal %d.\n", + current->comm, current->pid, signr); + +#ifdef __i386__ + printk("code at %08lx: ", regs->eip); + { + int i; + for (i = 0; i < 16; i++) { + unsigned char insn; + + __get_user(insn, (unsigned char *)(regs->eip + i)); + printk("%02x ", insn); + } + } +#endif + printk("\n"); + show_regs(regs); +} + +static int __init setup_print_fatal_signals(char *str) +{ + get_option (&str, &print_fatal_signals); + + return 1; +} + +__setup("print-fatal-signals=", setup_print_fatal_signals); static int specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t) @@ -819,7 +810,7 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t) action->sa.sa_handler = SIG_DFL; if (blocked) { sigdelset(&t->blocked, sig); - recalc_sigpending_tsk(t); + recalc_sigpending_and_wake(t); } } ret = specific_send_sig_info(sig, info, t); @@ -1006,17 +997,6 @@ void zap_other_threads(struct task_struct *p) if (t->exit_state) continue; - /* - * We don't want to notify the parent, since we are - * killed as part of a thread group due to another - * thread doing an execve() or similar. So set the - * exit signal to -1 to allow immediate reaping of - * the process. But don't detach the thread group - * leader. - */ - if (t != p->group_leader) - t->exit_signal = -1; - /* SIGKILL will be handled before any pending SIGSTOP */ sigaddset(&t->pending.signal, SIGKILL); signal_wake_up(t, 1); @@ -1093,42 +1073,21 @@ int kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp) return retval; } -int __kill_pg_info(int sig, struct siginfo *info, pid_t pgrp) -{ - if (pgrp <= 0) - return -EINVAL; - - return __kill_pgrp_info(sig, info, find_pid(pgrp)); -} - -int -kill_pg_info(int sig, struct siginfo *info, pid_t pgrp) -{ - int retval; - - read_lock(&tasklist_lock); - retval = __kill_pg_info(sig, info, pgrp); - read_unlock(&tasklist_lock); - - return retval; -} - int kill_pid_info(int sig, struct siginfo *info, struct pid *pid) { int error; - int acquired_tasklist_lock = 0; struct task_struct *p; rcu_read_lock(); - if (unlikely(sig_needs_tasklist(sig))) { + if (unlikely(sig_needs_tasklist(sig))) read_lock(&tasklist_lock); - acquired_tasklist_lock = 1; - } + p = pid_task(pid, PIDTYPE_PID); error = -ESRCH; if (p) error = group_send_sig_info(sig, info, p); - if (unlikely(acquired_tasklist_lock)) + + if (unlikely(sig_needs_tasklist(sig))) read_unlock(&tasklist_lock); rcu_read_unlock(); return error; @@ -1190,8 +1149,10 @@ EXPORT_SYMBOL_GPL(kill_pid_info_as_uid); static int kill_something_info(int sig, struct siginfo *info, int pid) { + int ret; + rcu_read_lock(); if (!pid) { - return kill_pg_info(sig, info, process_group(current)); + ret = kill_pgrp_info(sig, info, task_pgrp(current)); } else if (pid == -1) { int retval = 0, count = 0; struct task_struct * p; @@ -1206,12 +1167,14 @@ static int kill_something_info(int sig, struct siginfo *info, int pid) } } read_unlock(&tasklist_lock); - return count ? retval : -ESRCH; + ret = count ? retval : -ESRCH; } else if (pid < 0) { - return kill_pg_info(sig, info, -pid); + ret = kill_pgrp_info(sig, info, find_pid(-pid)); } else { - return kill_proc_info(sig, info, pid); + ret = kill_pid_info(sig, info, find_pid(pid)); } + rcu_read_unlock(); + return ret; } /* @@ -1310,12 +1273,6 @@ int kill_pid(struct pid *pid, int sig, int priv) EXPORT_SYMBOL(kill_pid); int -kill_pg(pid_t pgrp, int sig, int priv) -{ - return kill_pg_info(sig, __si_special(priv), pgrp); -} - -int kill_proc(pid_t pid, int sig, int priv) { return kill_proc_info(sig, __si_special(priv), pid); @@ -1397,6 +1354,11 @@ int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) ret = 1; goto out; } + /* + * Deliver the signal to listening signalfds. This must be called + * with the sighand lock held. + */ + signalfd_notify(p, sig); list_add_tail(&q->list, &p->pending.list); sigaddset(&p->pending.signal, sig); @@ -1440,6 +1402,11 @@ send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) q->info.si_overrun++; goto out; } + /* + * Deliver the signal to listening signalfds. This must be called + * with the sighand lock held. + */ + signalfd_notify(p, sig); /* * Put this signal on the shared-pending queue. @@ -1667,8 +1634,9 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info) /* * Queued signals ignored us while we were stopped for tracing. * So check for any that we should take before resuming user mode. + * This sets TIF_SIGPENDING, but never clears it. */ - recalc_sigpending(); + recalc_sigpending_tsk(current); } void ptrace_notify(int exit_code) @@ -1703,7 +1671,9 @@ finish_stop(int stop_count) read_unlock(&tasklist_lock); } - schedule(); + do { + schedule(); + } while (try_to_freeze()); /* * Now we don't run again until continued. */ @@ -1878,8 +1848,12 @@ relock: if (sig_kernel_ignore(signr)) /* Default is nothing. */ continue; - /* Init gets no signals it doesn't want. */ - if (current == child_reaper) + /* + * Init of a pid space gets no signals it doesn't want from + * within that pid space. It can of course get signals from + * its parent pid space. + */ + if (current == child_reaper(current)) continue; if (sig_kernel_stop(signr)) { @@ -1898,7 +1872,7 @@ relock: /* signals can be posted during this window */ - if (is_orphaned_pgrp(process_group(current))) + if (is_current_pgrp_orphaned()) goto relock; spin_lock_irq(¤t->sighand->siglock); @@ -1922,6 +1896,8 @@ relock: * Anything else is fatal, maybe with a core dump. */ current->flags |= PF_SIGNALED; + if ((signr != SIGKILL) && print_fatal_signals) + print_fatal_signal(regs, signr); if (sig_kernel_coredump(signr)) { /* * If it was able to dump core, this kills all @@ -1948,7 +1924,6 @@ EXPORT_SYMBOL(recalc_sigpending); EXPORT_SYMBOL_GPL(dequeue_signal); EXPORT_SYMBOL(flush_signals); EXPORT_SYMBOL(force_sig); -EXPORT_SYMBOL(kill_pg); EXPORT_SYMBOL(kill_proc); EXPORT_SYMBOL(ptrace_notify); EXPORT_SYMBOL(send_sig); @@ -2095,6 +2070,8 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from) /* * If you change siginfo_t structure, please be sure * this code is fixed accordingly. + * Please remember to update the signalfd_copyinfo() function + * inside fs/signalfd.c too, in case siginfo_t changes. * It should never copy any pad contained in the structure * to avoid security leaks, but must copy the generic * 3 ints plus the relevant union member. @@ -2275,7 +2252,7 @@ static int do_tkill(int tgid, int pid, int sig) * @pid: the PID of the thread * @sig: signal to be sent * - * This syscall also checks the tgid and returns -ESRCH even if the PID + * This syscall also checks the @tgid and returns -ESRCH even if the PID * exists but it's not belonging to the target process anymore. This * method solves the problem of threads exiting and PIDs getting reused. */ @@ -2365,7 +2342,7 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) rm_from_queue_full(&mask, &t->signal->shared_pending); do { rm_from_queue_full(&mask, &t->pending); - recalc_sigpending_tsk(t); + recalc_sigpending_and_wake(t); t = next_thread(t); } while (t != current); } @@ -2627,9 +2604,5 @@ __attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma) void __init signals_init(void) { - sigqueue_cachep = - kmem_cache_create("sigqueue", - sizeof(struct sigqueue), - __alignof__(struct sigqueue), - SLAB_PANIC, NULL, NULL); + sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC); }