[PATCH RFC v2 01/18] xfs: fix the error unwind in xfs_open_devices()

[Christian Brauner <brauner@kernel.org>]

Since the rt and log block devices are closed in xfs_free_buftarg() the
buftarg owns the device file. The error unwind does not respect that:
when the log buftarg allocation fails, out_free_rtdev_targ frees the rt
buftarg - releasing rtdev_file - and then falls through to
out_close_rtdev and releases it a second time.

The unwind also leaves mp->m_rtdev_targp and mp->m_ddev_targp pointing
to the freed buftargs. The failed mount continues into
deactivate_locked_super() -> xfs_kill_sb() -> xfs_mount_free(), which
frees them again.

Clear the buftarg pointers once the unwind freed them and clear
rtdev_file once the rt buftarg owns it, so nothing is released twice.

Reachable when a buftarg allocation fails after the data buftarg was
set up: an I/O error in sync_blockdev() or an allocation failure in
xfs_init_buftarg() while mounting with external rt and log devices.

Fixes: 41233576e9a4 ("xfs: close the RT and log block devices in xfs_free_buftarg")
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/xfs/xfs_super.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index eac7f9503805..8531d526fc44 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -534,8 +534,11 @@ xfs_open_devices(
  out_free_rtdev_targ:
 	if (mp->m_rtdev_targp)
 		xfs_free_buftarg(mp->m_rtdev_targp);
+	mp->m_rtdev_targp = NULL;
+	rtdev_file = NULL;	/* released by xfs_free_buftarg() */
  out_free_ddev_targ:
 	xfs_free_buftarg(mp->m_ddev_targp);
+	mp->m_ddev_targp = NULL;
  out_close_rtdev:
 	 if (rtdev_file)
 		bdev_fput(rtdev_file);

-- 
2.47.3