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Commit 6b2912ce authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 3b6e8204 7146db33

include/linux/signal.h

+1 −1
Original line number Diff line number Diff line
@@ -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))

kernel/signal.c

+59 −4
Original line number Diff line number Diff line
@@ -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 @@ bool get_signal(struct ksignal *ksig) 
		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;
@@ -2407,6 +2453,14 @@ bool get_signal(struct ksignal *ksig) 
			goto relock;

		}



		/*

		 * 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, &current->blocked, &ksig->info);



		if (!signr)
@@ -2489,6 +2543,7 @@ bool get_signal(struct ksignal *ksig) 
			continue;

		}



	fatal:

		spin_unlock_irq(&sighand->siglock);



		/*