[3.16.y-ckt stable] Patch "blk-mq: fix double-free in error path" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    blk-mq: fix double-free in error path

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From c5caff734425cddbb1efe801e88ce2a39fdb052b Mon Sep 17 00:00:00 2001
From: Tony Battersby <tonyb at cybernetics.com>
Date: Wed, 11 Feb 2015 11:32:30 -0500
Subject: blk-mq: fix double-free in error path

commit 564e559f2baf6a868768d0cac286980b3cfd6e30 upstream.

If the allocation of bt->bs fails, then bt->map can be freed twice, once
in blk_mq_init_bitmap_tags() -> bt_alloc(), and once in
blk_mq_init_bitmap_tags() -> bt_free().  Fix by setting the pointer to
NULL after the first free.

Signed-off-by: Tony Battersby <tonyb at cybernetics.com>
Signed-off-by: Jens Axboe <axboe at fb.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 block/blk-mq-tag.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 1caaa7c4605d..b88f4b375c27 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -511,6 +511,7 @@ static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth,
 	bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL);
 	if (!bt->bs) {
 		kfree(bt->map);
+		bt->map = NULL;
 		return -ENOMEM;
 	}