linux-ext4 - [PATCH 0/2] ext4: Fix possible fs corruption due to xattr races

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Date:   Mon,  6 Jun 2022 16:28:45 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ted Tso <tytso@....edu>
Cc:     <linux-ext4@...r.kernel.org>,
        Ritesh Harjani <ritesh.list@...il.com>, Jan Kara <jack@...e.cz>
Subject: [PATCH 0/2] ext4: Fix possible fs corruption due to xattr races

Hello,

I've tracked down the culprit of the jbd2 assertion Ritesh reported to me. In
the end it does not have much to do with jbd2 but rather points to a subtle
race in xattr code between xattr block reuse and xattr block freeing that can
result in fs corruption during journal replay. See patch 2/2 for more details.
These patches fix the problem. I have to say I'm not too happy with the special
mbcache interface I had to add because it just requires too deep knowledge of
how things work internally to get things right. If you get it wrong, you'll
have subtle races like above. But I didn't find a more transparent way to
fix this race. If someone has ideas, suggestions are welcome!

								Honza