[PATCH 3.18 077/151] blk-mq: fix double-free in error path

[Greg Kroah-Hartman]

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

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

From: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 block/blk-mq-tag.c |    1 +
 1 file changed, 1 insertion(+)

--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -500,6 +500,7 @@ static int bt_alloc(struct blk_mq_bitmap
 	bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL);
 	if (!bt->bs) {
 		kfree(bt->map);
+		bt->map = NULL;
 		return -ENOMEM;
 	}
 


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