From a41b816c174409417d91b4ceef0145c9f0bef67c Mon Sep 17 00:00:00 2001 From: Joseph Qi Date: Wed, 7 Jun 2017 11:36:14 +0800 Subject: [PATCH] blk-throttle: fix NULL pointer dereference in throtl_schedule_pending_timer I have encountered a NULL pointer dereference in throtl_schedule_pending_timer: [ 413.735396] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 [ 413.735535] IP: [] throtl_schedule_pending_timer+0x3f/0x210 [ 413.735643] PGD 22c8cf067 PUD 22cb34067 PMD 0 [ 413.735713] Oops: 0000 [#1] SMP ...... This is caused by the following case: blk_throtl_bio throtl_schedule_next_dispatch <= sq is top level one without parent throtl_schedule_pending_timer sq_to_tg(sq)->td->throtl_slice <= sq_to_tg(sq) returns NULL Fix it by using sq_to_td instead of sq_to_tg(sq)->td, which will always return a valid td. Fixes: 297e3d854784 ("blk-throttle: make throtl_slice tunable") Signed-off-by: Joseph Qi Reviewed-by: Shaohua Li Signed-off-by: Jens Axboe --- block/blk-throttle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index fc13dd0c6e39..3b751f706c61 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -698,7 +698,7 @@ static void throtl_dequeue_tg(struct throtl_grp *tg) static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, unsigned long expires) { - unsigned long max_expire = jiffies + 8 * sq_to_tg(sq)->td->throtl_slice; + unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice; /* * Since we are adjusting the throttle limit dynamically, the sleep -- 2.30.2