From: Liu Bo <bo.liu@linux.alibaba.com>
Date: Tue, 29 May 2018 16:29:12 +0800
Subject: [PATCH] blk-throttle: fix potential NULL pointer dereference in
Git-commit: 2ab74cd29622c48e9852d85618081c061b6ac6d9
Patch-mainline: v4.18-rc1
References: bsc#1104967,FATE#325924
 throtl_select_dispatch

tg in throtl_select_dispatch is used first and then do check. Since tg
may be NULL, it has potential NULL pointer dereference risk. So fix
it.

Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-throttle.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f63d88c92c3a..35bed770664d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1207,7 +1207,7 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
 
 	while (1) {
 		struct throtl_grp *tg = throtl_rb_first(parent_sq);
-		struct throtl_service_queue *sq = &tg->service_queue;
+		struct throtl_service_queue *sq;
 
 		if (!tg)
 			break;
@@ -1219,6 +1219,7 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
 
 		nr_disp += throtl_dispatch_tg(tg);
 
+		sq = &tg->service_queue;
 		if (sq->nr_queued[0] || sq->nr_queued[1])
 			tg_update_disptime(tg);
 
-- 
2.16.4