Commit b74d0deb authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds
Browse files

Restrict clearing TIF_SIGPENDING 



This patch should get a few birds.  It prevents sigaction calls from
clearing TIF_SIGPENDING in other threads, which could leak -ERESTART*.
And It fixes ptrace_stop not to clear it, which done at the syscall exit
stop could leak -ERESTART*.  It probably removes the harm from signalfd,
at least assuming it never calls dequeue_signal on kernel threads that
might have used block_all_signals.

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8381e04b

kernel/signal.c

+12 −4
Original line number Diff line number Diff line
@@ -105,7 +105,11 @@ static int recalc_sigpending_tsk(struct task_struct *t) 
		set_tsk_thread_flag(t, TIF_SIGPENDING);

		return 1;

	}

	clear_tsk_thread_flag(t, TIF_SIGPENDING);

	/*

	 * 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;

}
@@ -121,7 +125,9 @@ void recalc_sigpending_and_wake(struct task_struct *t) 


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. */
@@ -385,7 +391,8 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) 
			}

		}

	}

	recalc_sigpending_tsk(tsk);

	if (likely(tsk == current))

		recalc_sigpending();

	if (signr && unlikely(sig_kernel_stop(signr))) {

		/*

		 * Set a marker that we have dequeued a stop signal.  Our
@@ -1580,8 +1587,9 @@ 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)

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