linux-kernel - [patch -next] blk-mq: NULL dereference in __blk_mq_alloc_rq

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Date:	Sat, 13 Sep 2014 11:09:28 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	"Elliott, Robert (Server Storage)" <Elliott@...com>
Subject: [patch -next] blk-mq: NULL dereference in __blk_mq_alloc_rq_maps()

We shouldn't set "set->tags" to NULL here because if we return -ENOMEM
here then we call the function a second time.  On the second time
through the loop then the statement:

	set->tags[i] = blk_mq_init_rq_map(set, i);

will Oops.  Also it is a memory leak and a layering violation.  There is
a correct call to kfree(set->tags) in blk_mq_alloc_tag_set().

Fixes: a516440542af ('blk-mq: scale depth and rq map appropriate if low on memory')
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3d863df..7e7ca57 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1961,7 +1961,6 @@ out_unwind:
 	while (--i >= 0)
 		blk_mq_free_rq_map(set, set->tags[i], i);
 
-	set->tags = NULL;
 	return -ENOMEM;
 }
 
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