linux-kernel - [PATCH v2 6/6] block: skip queue if NULL on blk_cleanup

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Message-Id: <20210715045531.420201-7-mcgrof@kernel.org>
Date:   Wed, 14 Jul 2021 21:55:31 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     axboe@...nel.dk
Cc:     hare@...e.de, bvanassche@....org, ming.lei@...hat.com,
        hch@...radead.org, jack@...e.cz, osandov@...com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: [PATCH v2 6/6] block: skip queue if NULL on blk_cleanup_queue()

Now that error handling for add_disk*() calls is added, we must
accept a common form for when errors are detected on the the
add_disk*() calls, and that is to call blk_cleanup_disk() on
error always. One of the corner cases possible is a driver bug
where the queue is already gone and we cannot blk_get_queue(),
and so may be NULL. When blk_cleanup_disk() is called in this
case blk_cleanup_queue() will crash with a null dereference.

Make this an accepted condition and just skip it. This allows us
to also test for it safely with error injection.

Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 block/blk-core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-core.c b/block/blk-core.c
index 04477697ee4b..156f7d3b4bd9 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -372,6 +372,9 @@ void blk_cleanup_queue(struct request_queue *q)
 	/* cannot be called from atomic context */
 	might_sleep();

+	if (!q)
+		return;
+
 	WARN_ON_ONCE(blk_queue_registered(q));

 	/* mark @q DYING, no new request or merges will be allowed afterwards */
-- 
2.27.0