linux-kernel - [PATCH 4.18 013/158] block: bfq: swap puts in bfqg_and_blkg

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Message-Id: <20180917211711.318678529@linuxfoundation.org>
Date:   Tue, 18 Sep 2018 00:40:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paolo Valente <paolo.valente@...aro.org>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.18 013/158] block: bfq: swap puts in bfqg_and_blkg_put

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

commit d5274b3cd6a814ccb2f56d81ee87cbbf51bd4cf7 upstream.

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

Fixes: 8f9bebc33dd7 ("block, bfq: access and cache blkg data only when safe")
Acked-by: Paolo Valente <paolo.valente@...aro.org>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/bfq-cgroup.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -275,9 +275,9 @@ static void bfqg_and_blkg_get(struct bfq
 
 void bfqg_and_blkg_put(struct bfq_group *bfqg)
 {
-	bfqg_put(bfqg);
-
 	blkg_put(bfqg_to_blkg(bfqg));
+
+	bfqg_put(bfqg);
 }
 
 /* @stats = 0 */