linux-kernel - [PATCH] blk-mq-sched: Don't reference queue tagset in blk_mq_sched_tags

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Date:   Fri, 22 Oct 2021 16:12:20 +0800
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>
CC:     <ming.lei@...hat.com>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <naresh.kamboju@...aro.org>,
        <anders.roxell@...aro.org>, <arnd@...db.de>,
        John Garry <john.garry@...wei.com>
Subject: [PATCH] blk-mq-sched: Don't reference queue tagset in blk_mq_sched_tags_teardown()

We should not reference the queue tagset in blk_mq_sched_tags_teardown()
(see function comment) for the blk-mq flags, so use the passed flags
instead.

This solves a use-after-free, similarly fixed earlier (and since broken
again) in commit f0c1c4d2864e ("blk-mq: fix use-after-free in
blk_mq_exit_sched").

Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Tested-by: Anders Roxell <anders.roxell@...aro.org>
Fixes: e155b0c238b2 ("blk-mq: Use shared tags for shared sbitmap support")
Signed-off-by: John Garry <john.garry@...wei.com>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index e85b7556b096..6a9444848e3a 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -541,7 +541,7 @@ static void blk_mq_sched_tags_teardown(struct request_queue *q, unsigned int fla
 
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (hctx->sched_tags) {
-			if (!blk_mq_is_shared_tags(q->tag_set->flags))
+			if (!blk_mq_is_shared_tags(flags))
 				blk_mq_free_rq_map(hctx->sched_tags);
 			hctx->sched_tags = NULL;
 		}
-- 
2.17.1