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

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

From: Omar Sandoval <osan...@fb.com>


[ Upstream commit 6bf6b0aa3da84a3d9126919a94c49c0fb7ee2fb3 ]

If blk_mq_init_queue() returns an error, it gets assigned to
vblk->disk->queue. Then, when we call put_disk(), we end up calling
blk_put_queue() with the ERR_PTR, causing a bad dereference. Fix it by
only assigning to vblk->disk->queue on success.

Signed-off-by: Omar Sandoval <osan...@fb.com>
Reviewed-by: Jeff Moyer <jmo...@redhat.com>
Signed-off-by: Jens Axboe <ax...@fb.com>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/block/virtio_blk.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -641,11 +641,12 @@ static int virtblk_probe(struct virtio_d
        if (err)
                goto out_put_disk;
 
-       q = vblk->disk->queue = blk_mq_init_queue(&vblk->tag_set);
+       q = blk_mq_init_queue(&vblk->tag_set);
        if (IS_ERR(q)) {
                err = -ENOMEM;
                goto out_free_tags;
        }
+       vblk->disk->queue = q;
 
        q->queuedata = vblk;
 


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