linux-kernel - Re: [PATCH 1/1] ext4: fix crash on BUG_ON in ext4_alloc_group

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Message-ID: <7521d6a5-eb58-4418-8c2a-a9950d8faf9c@sandeen.net>
Date: Thu, 26 Sep 2024 11:29:57 -0500
From: Eric Sandeen <sandeen@...deen.net>
To: Baokun Li <libaokun1@...wei.com>, Jan Kara <jack@...e.cz>,
 Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Cc: tytso@....edu, stable@...r.kernel.org,
 Andreas Dilger <adilger.kernel@...ger.ca>,
 Stéphane Graber <stgraber@...raber.org>,
 Christian Brauner <brauner@...nel.org>, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 Wesley Hershberger <wesley.hershberger@...onical.com>,
 Yang Erkun <yangerkun@...wei.com>
Subject: Re: [PATCH 1/1] ext4: fix crash on BUG_ON in ext4_alloc_group_tables

On 9/26/24 11:04 AM, Eric Sandeen wrote:

 
> Can you explain what the 2 cases under
> 
> /* Avoid allocating large 'groups' array if not needed */
> 
> are doing? I *think* the first 'if' is trying not to over-allocate for the last
> batch of block groups that get added during a resize. What is the "else if" case
> doing?

(or maybe I had that backwards)

Incidentally, the offending commit that this fixes (665d3e0af4d35ac) got turned
into CVE-2023-52622, so it's quite likely that distros have backported the broken
commit as part of the CVE game.

So the followup fix looks a bit urgent to me.

-Eric