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Re: [PATCH] xfs: growfs overruns AGFL buffer on V4 filesystems

To: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: [PATCH] xfs: growfs overruns AGFL buffer on V4 filesystems
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Thu, 21 Nov 2013 13:42:39 +0800
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1385008866-22256-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1385008866-22256-1-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0
On 11/21 2013 12:41, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> This loop in xfs_growfs_data_private() is incorrect for V4
> superblocks filesystems:
> 
>               for (bucket = 0; bucket < XFS_AGFL_SIZE(mp); bucket++)
>                       agfl->agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);
> 
> For V4 filesystems, we don't have a agfl header structure, and so
> XFS_AGFL_SIZE() returns an entire sector's worth of entries, which
> we then index from an offset into the sector. Hence: buffer overrun.
> 
> This problem was introduced in 3.10 by commit 77c95bba ("xfs: add
> CRC checks to the AGFL") which changed the AGFL structure but failed
> to update the growfs code to handle the different structures.
> 
> Fix it by using the correct offset into the buffer for both V4 and
> V5 filesystems.
This is a problem I'm able to understand.

Reviewed-by: Jie Liu <jeff.liu@xxxxxxxxxx>

Thanks,
-Jeff

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