This is a note to let you know that I've just added the patch titled
Fix use after free in get_tree_bdev()
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fix-use-after-free-in-get_tree_bdev.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From dd7bc8158b413e0b580c491e8bd18cb91057c7c2 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@xxxxxxxxxx>
Date: Tue, 28 Apr 2020 21:27:48 +0100
Subject: Fix use after free in get_tree_bdev()
From: David Howells <dhowells@xxxxxxxxxx>
commit dd7bc8158b413e0b580c491e8bd18cb91057c7c2 upstream.
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@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Ian Kent <raven@xxxxxxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- 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;
}
Patches currently in stable-queue which might be from dhowells@xxxxxxxxxx are
queue-5.4/fix-use-after-free-in-get_tree_bdev.patch
