[XFS] fix use after free with external logs or real-time devices

SGI-PV: 983806

SGI-Modid: xfs-linux-melb:xfs-kern:31666a

Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index b40086680047..30ae96397e31 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -792,12 +792,14 @@ xfs_close_devices(
         struct xfs_mount        *mp)
 {
         if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) {
+                struct block_device *logdev = mp->m_logdev_targp->bt_bdev;
                 xfs_free_buftarg(mp->m_logdev_targp);
-                xfs_blkdev_put(mp->m_logdev_targp->bt_bdev);
+                xfs_blkdev_put(logdev);
         }
         if (mp->m_rtdev_targp) {
+                struct block_device *rtdev = mp->m_rtdev_targp->bt_bdev;
                 xfs_free_buftarg(mp->m_rtdev_targp);
-                xfs_blkdev_put(mp->m_rtdev_targp->bt_bdev);
+                xfs_blkdev_put(rtdev);
         }
         xfs_free_buftarg(mp->m_ddev_targp);
 }