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

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Message-ID: <11e3133e-6069-477f-9c4a-3698bd6a18ec@huawei.com>
Date: Fri, 27 Sep 2024 09:51:58 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Eric Sandeen <sandeen@...deen.net>
CC: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>,
	<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>, Jan
 Kara <jack@...e.cz>, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 1/1] ext4: fix crash on BUG_ON in ext4_alloc_group_tables

On 2024/9/27 0:29, Eric Sandeen wrote:
> 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.
The commit to fix CVE-2023-52622 is commit 5d1935ac02ca5a
("ext4: avoid online resizing failures due to oversized flex bg").
This commit does not address the off by one issue above.
>
> So the followup fix looks a bit urgent to me.
>
> -Eric
Okay, I'll send out the fix patch today.

Regards,
Baokun
.