linux-kernel - Re: [PATCH v2] ext4: check if offset+length is valid in fallocate

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Message-ID: <21f3fd84-2de9-646c-4d0c-94007a996c70@linaro.org>
Date:   Mon, 28 Mar 2022 09:12:27 -0700
From:   Tadeusz Struk <tadeusz.struk@...aro.org>
To:     linux-ext4@...r.kernel.org
Cc:     Andreas Dilger <adilger.kernel@...ger.ca>,
        Ritesh Harjani <riteshh@...ux.ibm.com>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+7a806094edd5d07ba029@...kaller.appspotmail.com,
        tytso@....edu
Subject: Re: [PATCH v2] ext4: check if offset+length is valid in fallocate

On 3/15/22 14:54, Tadeusz Struk wrote:
> Syzbot found an issue [1] in ext4_fallocate().
> The C reproducer [2] calls fallocate(), passing size 0xffeffeff000ul,
> and offset 0x1000000ul, which, when added together exceed the disk size,
> and trigger a BUG in ext4_ind_remove_space() [3].
> According to the comment doc in ext4_ind_remove_space() the 'end' block
> parameter needs to be one block after the last block to remove.
> In the case when the BUG is triggered it points to the last block on
> a 4GB virtual disk image. This is calculated in
> ext4_ind_remove_space() in [4].
> This patch adds a check that ensure the length + offest to be
> within the valid range and returns -ENOSPC error code in case
> it is invalid.

Hi,
Any feedback on this?

-- 
Thanks,
Tadeusz