Re: [PATCH stable] ubifs: Handle re-linking of inodes correctly while recovery

[Sasha Levin <sashal@kernel.org>]

On Wed, Dec 26, 2018 at 01:32:11PM +0100, Rafał Miłecki wrote:
>From: Richard Weinberger <richard@nod.at>
>
>commit e58725d51fa8da9133f3f1c54170aa2e43056b91 upstream.
>
>UBIFS's recovery code strictly assumes that a deleted inode will never
>come back, therefore it removes all data which belongs to that inode
>as soon it faces an inode with link count 0 in the replay list.
>Before O_TMPFILE this assumption was perfectly fine. With O_TMPFILE
>it can lead to data loss upon a power-cut.
>
>Consider a journal with entries like:
>0: inode X (nlink = 0) /* O_TMPFILE was created */
>1: data for inode X /* Someone writes to the temp file */
>2: inode X (nlink = 0) /* inode was changed, xattr, chmod, … */
>3: inode X (nlink = 1) /* inode was re-linked via linkat() */
>
>Upon replay of entry #2 UBIFS will drop all data that belongs to inode X,
>this will lead to an empty file after mounting.
>
>As solution for this problem, scan the replay list for a re-link entry
>before dropping data.
>
>Fixes: 474b93704f32 ("ubifs: Implement O_TMPFILE")
>Cc: stable@vger.kernel.org # 4.9-4.18
>Cc: Russell Senior <russell@personaltelco.net>
>Cc: Rafał Miłecki <zajec5@gmail.com>
>Reported-by: Russell Senior <russell@personaltelco.net>
>Reported-by: Rafał Miłecki <zajec5@gmail.com>
>Tested-by: Rafał Miłecki <rafal@milecki.pl>
>Signed-off-by: Richard Weinberger <richard@nod.at>
>[rmilecki: update ubifs_assert() calls to compile with 4.18 and older]
>Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
>(cherry picked from commit e58725d51fa8da9133f3f1c54170aa2e43056b91)

Queued for 4.14 and 4.9, thank you.

--
Thanks,
Sasha