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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-08 15:39:28 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-08 15:39:28 -0800 |
commit | 6b2912cedc238c984e6a4039836ed9c911121076 (patch) | |
tree | a5d324da84ec81b43602b96023943e8f027b1943 | |
parent | 3b6e8204a997510718949fd177f01da1860c738a (diff) | |
parent | 7146db3317c67b517258cb5e1b08af387da0618b (diff) | |
download | lwn-6b2912cedc238c984e6a4039836ed9c911121076.tar.gz lwn-6b2912cedc238c984e6a4039836ed9c911121076.zip |
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull signal fixes from Eric Biederman:
"This contains four small fixes for signal handling. A missing range
check, a regression fix, prioritizing signals we have already started
a signal group exit for, and better detection of synchronous signals.
The confused decision of which signals to handle failed spectacularly
when a timer was pointed at SIGBUS and the stack overflowed. Resulting
in an unkillable process in an infinite loop instead of a SIGSEGV and
core dump"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
signal: Better detection of synchronous signals
signal: Always notice exiting tasks
signal: Always attempt to allocate siginfo for SIGSTOP
signal: Make siginmask safe when passed a signal of 0
-rw-r--r-- | include/linux/signal.h | 2 | ||||
-rw-r--r-- | kernel/signal.c | 63 |
2 files changed, 60 insertions, 5 deletions
diff --git a/include/linux/signal.h b/include/linux/signal.h index cc7e2c1cd444..9702016734b1 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -392,7 +392,7 @@ extern bool unhandled_signal(struct task_struct *tsk, int sig); #endif #define siginmask(sig, mask) \ - ((sig) < SIGRTMIN && (rt_sigmask(sig) & (mask))) + ((sig) > 0 && (sig) < SIGRTMIN && (rt_sigmask(sig) & (mask))) #define SIG_KERNEL_ONLY_MASK (\ rt_sigmask(SIGKILL) | rt_sigmask(SIGSTOP)) diff --git a/kernel/signal.c b/kernel/signal.c index e1d7ad8e6ab1..99fa8ff06fd9 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -688,6 +688,48 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, kernel_siginfo_t *in } EXPORT_SYMBOL_GPL(dequeue_signal); +static int dequeue_synchronous_signal(kernel_siginfo_t *info) +{ + struct task_struct *tsk = current; + struct sigpending *pending = &tsk->pending; + struct sigqueue *q, *sync = NULL; + + /* + * Might a synchronous signal be in the queue? + */ + if (!((pending->signal.sig[0] & ~tsk->blocked.sig[0]) & SYNCHRONOUS_MASK)) + return 0; + + /* + * Return the first synchronous signal in the queue. + */ + list_for_each_entry(q, &pending->list, list) { + /* Synchronous signals have a postive si_code */ + if ((q->info.si_code > SI_USER) && + (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK)) { + sync = q; + goto next; + } + } + return 0; +next: + /* + * Check if there is another siginfo for the same signal. + */ + list_for_each_entry_continue(q, &pending->list, list) { + if (q->info.si_signo == sync->info.si_signo) + goto still_pending; + } + + sigdelset(&pending->signal, sync->info.si_signo); + recalc_sigpending(); +still_pending: + list_del_init(&sync->list); + copy_siginfo(info, &sync->info); + __sigqueue_free(sync); + return info->si_signo; +} + /* * Tell a process that it has a new active signal.. * @@ -1057,10 +1099,9 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc result = TRACE_SIGNAL_DELIVERED; /* - * Skip useless siginfo allocation for SIGKILL SIGSTOP, - * and kernel threads. + * Skip useless siginfo allocation for SIGKILL and kernel threads. */ - if (sig_kernel_only(sig) || (t->flags & PF_KTHREAD)) + if ((sig == SIGKILL) || (t->flags & PF_KTHREAD)) goto out_set; /* @@ -2394,6 +2435,11 @@ relock: goto relock; } + /* Has this task already been marked for death? */ + ksig->info.si_signo = signr = SIGKILL; + if (signal_group_exit(signal)) + goto fatal; + for (;;) { struct k_sigaction *ka; @@ -2407,7 +2453,15 @@ relock: goto relock; } - signr = dequeue_signal(current, ¤t->blocked, &ksig->info); + /* + * Signals generated by the execution of an instruction + * need to be delivered before any other pending signals + * so that the instruction pointer in the signal stack + * frame points to the faulting instruction. + */ + signr = dequeue_synchronous_signal(&ksig->info); + if (!signr) + signr = dequeue_signal(current, ¤t->blocked, &ksig->info); if (!signr) break; /* will return 0 */ @@ -2489,6 +2543,7 @@ relock: continue; } + fatal: spin_unlock_irq(&sighand->siglock); /* |