block: bfq: swap puts in bfqg_and_blkg_put

koct9i · axboe · commit d5274b3cd6a8 · 2018-09-06T11:32:58.000-06:00
Fix trivial use-after-free. This could be last reference to bfqg. Fixes: 8f9bebc ("block, bfq: access and cache blkg data only when safe") Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
@@ -275,9 +275,9 @@ static void bfqg_and_blkg_get(struct bfq_group *bfqg)
 
 void bfqg_and_blkg_put(struct bfq_group *bfqg)
 {
-	bfqg_put(bfqg);
-
 	blkg_put(bfqg_to_blkg(bfqg));
+
+	bfqg_put(bfqg);
 }
 
 /* @stats = 0 */

Original file line number	Diff line number	Diff line change
`@@ -275,9 +275,9 @@ static void bfqg_and_blkg_get(struct bfq_group *bfqg)`
`275`	`275`
`276`	`276`	`void bfqg_and_blkg_put(struct bfq_group *bfqg)`
`277`	`277`	`{`
`278`		`- bfqg_put(bfqg);`
`279`		`-`
`280`	`278`	`blkg_put(bfqg_to_blkg(bfqg));`
	`279`	`+`
	`280`	`+ bfqg_put(bfqg);`
`281`	`281`	`}`
`282`	`282`
`283`	`283`	`/* @stats = 0 */`