[Qemu-devel] [PATCH] timer: a9gtimer: check auto-increment register value

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

ARM A9MP processor has a peripheral timer with an auto-increment
register, which holds an increment step value. A user could set
this value to zero, when auto-increment control bit is enabled.
This leads to an infinite loop in 'a9_gtimer_update' while
updating comparator value. Add check to avoid it.

Reported-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/timer/a9gtimer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/timer/a9gtimer.c b/hw/timer/a9gtimer.c
index 772f85f..3f752ce 100644
--- a/hw/timer/a9gtimer.c
+++ b/hw/timer/a9gtimer.c
@@ -85,7 +85,7 @@ static void a9_gtimer_update(A9GTimerState *s, bool sync)
             while (gtb->compare < update.new) {
                 DB_PRINT("Compare event happened for CPU %d\n", i);
                 gtb->status = 1;
-                if (gtb->control & R_CONTROL_AUTO_INCREMENT) {
+                if (gtb->inc && gtb->control & R_CONTROL_AUTO_INCREMENT) {
                     DB_PRINT("Auto incrementing timer compare by %" PRId32 "\n",
                              gtb->inc);
                     gtb->compare += gtb->inc;
-- 
2.5.5