linux-kernel - Re: [PATCH v2] ext4: fix a NULL pointer when validating an inode bitmap

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Message-ID: <Y4U18wly7K87fX9v@mit.edu>
Date:   Mon, 28 Nov 2022 17:28:03 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     Luís Henriques <lhenriques@...e.de>
Cc:     Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] ext4: fix a NULL pointer when validating an inode
 bitmap

On Tue, Nov 08, 2022 at 02:06:29PM +0000, Luís Henriques wrote:
> > What makes you believe that?  Look at how s_group_info is initialized
> > in ext4_mb_alloc_groupinfo() in fs/ext4/mballoc.c.  It's pretty
> > careful to make sure this is not the case.
> 
> Right.  I may be missing something, but I don't think we get that far.
> __ext4_fill_super() will first call ext4_setup_system_zone() (which is
> where this bug occurs) and only after that ext4_mb_init() will be invoked
> (which is where ext4_mb_alloc_groupinfo() will eventually be called).

I finally got around to taking a closer look at this, and I have a
much better understandign of what is going on.  For more details, and
a suggested fix, please see:

     https://bugzilla.kernel.org/show_bug.cgi?id=216541#c1

						- Ted