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 <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Brad Spengler <[email protected]>
Cc: PaX Team <[email protected]>
Cc: <[email protected]> # 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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