dm: do not reuse dm_blk_ioctl block_device input as local variable

(Ab)using the @bdev passed to dm_blk_ioctl() opens the potential for
targets' .prepare_ioctl to fail if they go on to check the bdev for
!NULL.

Fixes: e56f81e0b01e ("dm: refactor ioctl handling")
Reported-by: Junichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index fabd5d8fd559..5df40480228b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -603,9 +603,10 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
 {
         struct mapped_device *md = bdev->bd_disk->private_data;
         struct dm_target *tgt;
+        struct block_device *tgt_bdev = NULL;
         int srcu_idx, r;
 
-        r = dm_get_live_table_for_ioctl(md, &tgt, &bdev, &mode, &srcu_idx);
+        r = dm_get_live_table_for_ioctl(md, &tgt, &tgt_bdev, &mode, &srcu_idx);
         if (r < 0)
                 return r;
 
@@ -620,7 +621,7 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
                         goto out;
         }
 
-        r =  __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+        r =  __blkdev_driver_ioctl(tgt_bdev, mode, cmd, arg);
 out:
         dm_put_live_table(md, srcu_idx);
         return r;