[PATCH 056/139] posix-cpu-timers: Fix nanosleep task_struct leak

[Luis Henriques]

3.5.7.7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stanislaw Gruszka <sgruszka at redhat.com>

commit e6c42c295e071dd74a66b5a9fcf4f44049888ed8 upstream.

The trinity fuzzer triggered a task_struct reference leak via
clock_nanosleep with CPU_TIMERs. do_cpu_nanosleep() calls
posic_cpu_timer_create(), but misses a corresponding
posix_cpu_timer_del() which leads to the task_struct reference leak.

Reported-and-tested-by: Tommi Rantala <tt.rantala at gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
Cc: Dave Jones <davej at redhat.com>
Cc: John Stultz <john.stultz at linaro.org>
Cc: Oleg Nesterov <oleg at redhat.com>
Link: http://lkml.kernel.org/r/20130215100810.GF4392@redhat.com
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/posix-cpu-timers.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 125cb67..acbb79c 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1422,8 +1422,10 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
 		while (!signal_pending(current)) {
 			if (timer.it.cpu.expires.sched == 0) {
 				/*
-				 * Our timer fired and was reset.
+				 * Our timer fired and was reset, below
+				 * deletion can not fail.
 				 */
+				posix_cpu_timer_del(&timer);
 				spin_unlock_irq(&timer.it_lock);
 				return 0;
 			}
@@ -1441,9 +1443,26 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
 		 * We were interrupted by a signal.
 		 */
 		sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
-		posix_cpu_timer_set(&timer, 0, &zero_it, it);
+		error = posix_cpu_timer_set(&timer, 0, &zero_it, it);
+		if (!error) {
+			/*
+			 * Timer is now unarmed, deletion can not fail.
+			 */
+			posix_cpu_timer_del(&timer);
+		}
 		spin_unlock_irq(&timer.it_lock);
 
+		while (error == TIMER_RETRY) {
+			/*
+			 * We need to handle case when timer was or is in the
+			 * middle of firing. In other cases we already freed
+			 * resources.
+			 */
+			spin_lock_irq(&timer.it_lock);
+			error = posix_cpu_timer_del(&timer);
+			spin_unlock_irq(&timer.it_lock);
+		}
+
 		if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
 			/*
 			 * It actually did fire already.
-- 
1.8.1.2