linux-kernel - [PATCH] block: bfq: swap puts in bfqg_and_blkg

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Message-ID: <153622114435.533797.15694137158197822778.stgit@buzz>
Date:   Thu, 06 Sep 2018 11:05:44 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Paolo Valente <paolo.valente@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] block: bfq: swap puts in bfqg_and_blkg_put

Fix trivial use-after-free. This could be last reference to bfqg.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Fixes: 8f9bebc33dd7 ("block, bfq: access and cache blkg data only when safe")
---
 block/bfq-cgroup.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 58c6efa9f9a9..9fe5952d117d 100644
--- 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 */