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Restrict clearing TIF_SIGPENDING

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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: Roland 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: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2007-06-06 03:59:00 -07:00 committed by Linus Torvalds
parent 8381e04b90
commit b74d0deb96
1 changed files with 12 additions and 4 deletions
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16
kernel/signal.c
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@ -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)