posix-cpu-timers: Fix nanosleep task_struct leak

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@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20130215100810.GF4392@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index a278cad1d5d6225a52e6bf00b2fd90f98bbe916e..942ca27a28b7ca81ed7556c496fa6ea40eeb556e 100644 (file)
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1401,8 +1401,10 @@ 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;
                        }
@@ -1420,9 +1422,26 @@ 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.