Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
* [PATCH AUTOSEL 5.4 29/35] Fix use after free in get_tree_bdev()
       [not found] <20200507142830.26239-1-sashal@kernel.org>
@ 2020-05-07 14:28 ` Sasha Levin
  0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2020-05-07 14:28 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: David Howells, Lukas Czerner, Ian Kent, Al Viro, Linus Torvalds,
	Sasha Levin, linux-fsdevel

From: David Howells <dhowells@redhat.com>

[ Upstream commit dd7bc8158b413e0b580c491e8bd18cb91057c7c2 ]

Commit 6fcf0c72e4b9, a fix to get_tree_bdev() put a missing blkdev_put() in
the wrong place, before a warnf() that displays the bdev under
consideration rather after it.

This results in a silent lockup in printk("%pg") called via warnf() from
get_tree_bdev() under some circumstances when there's a race with the
blockdev being frozen.  This can be caused by xfstests/tests/generic/085 in
combination with Lukas Czerner's ext4 mount API conversion patchset.  It
looks like it ought to occur with other users of get_tree_bdev() such as
XFS, but apparently doesn't.

Fix this by switching the order of the lines.

Fixes: 6fcf0c72e4b9 ("vfs: add missing blkdev_put() in get_tree_bdev()")
Reported-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Ian Kent <raven@themaw.net>
cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/super.c b/fs/super.c
index cd352530eca90..a288cd60d2aed 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1302,8 +1302,8 @@ int get_tree_bdev(struct fs_context *fc,
 	mutex_lock(&bdev->bd_fsfreeze_mutex);
 	if (bdev->bd_fsfreeze_count > 0) {
 		mutex_unlock(&bdev->bd_fsfreeze_mutex);
-		blkdev_put(bdev, mode);
 		warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
+		blkdev_put(bdev, mode);
 		return -EBUSY;
 	}
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] only message in thread

only message in thread, other threads:[~2020-05-07 14:34 UTC | newest]

Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <20200507142830.26239-1-sashal@kernel.org>
2020-05-07 14:28 ` [PATCH AUTOSEL 5.4 29/35] Fix use after free in get_tree_bdev() Sasha Levin

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).