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| author | Roland McGrath <roland@redhat.com> | 2007-06-06 03:59:00 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-06-07 08:52:15 -0700 |
| commit | b74d0deb968e1f85942f17080eace015ce3c332c (patch) | |
| tree | 7db612ba2931ef22ff7166f51dcb0fd1fe1d7ee1 /kernel | |
| parent | 8381e04b90ce9e7669a2d20aa7aaff3be910e447 (diff) | |
| download | lwn-b74d0deb968e1f85942f17080eace015ce3c332c.tar.gz lwn-b74d0deb968e1f85942f17080eace015ce3c332c.zip | |
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: 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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/signal.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index acdfc0549c6f..fe590e00db8d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -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) |