Messages in this thread Patch in this message | | | From | Mathias Krause <> | Subject | [PATCH] posix-timers: fix stack info leak in timer_create() | Date | Sat, 4 Oct 2014 23:06:39 +0200 |
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If userland creates a timer without specifying a sigevent info, we'll create one ourself, using a stack local variable. Particularly will we use the timer ID as sival_int. But as sigev_value is a union containing a pointer and an int, that assignment will only partially initialize sigev_value on systems where the size of a pointer is bigger than the size of an int. On such systems we'll copy the uninitialized stack bytes from the timer_create() call to userland when the timer actually fires and we're going to deliver the signal.
Initialize sigev_value with 0 to plug the stack info leak.
Found in the PaX patch, written by the PaX Team.
Fixes: 5a9fa7307285 ("posix-timers: kill ->it_sigev_signo and...") Signed-off-by: Mathias Krause <minipli@googlemail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Brad Spengler <spender@grsecurity.net> Cc: PaX Team <pageexec@freemail.hu> Cc: <stable@vger.kernel.org> # v2.6.28+ --- kernel/time/posix-timers.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 42b463ad90f2..31ea01f42e1f 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -636,6 +636,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock, goto out; } } else { + memset(&event.sigev_value, 0, sizeof(event.sigev_value)); event.sigev_notify = SIGEV_SIGNAL; event.sigev_signo = SIGALRM; event.sigev_value.sival_int = new_timer->it_id; -- 1.7.10.4
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