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Re: [PATCH] xfs: fix possible overflow in xfs_ioc_trim()

To: Lukas Czerner <lczerner@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: fix possible overflow in xfs_ioc_trim()
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 6 Sep 2011 10:02:38 -0400
Cc: xfs@xxxxxxxxxxx, hch@xxxxxxxxxxxxx
In-reply-to: <1315233205-27093-1-git-send-email-lczerner@xxxxxxxxxx>
References: <1315233205-27093-1-git-send-email-lczerner@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Sep 05, 2011 at 04:33:25PM +0200, Lukas Czerner wrote:
> In xfs_ioc_trim it is possible that start+len might overflow. Fix it by
> decrementing the len so that start+len equals to the file system size in
> the worst case.

The idea of the check looks reasonable, but I think it needs to be done
a bit different.  Was this caught by the new testcase you just sent?

> +     xfs_fsblock_t           max_blks =  XFS_MAX_DBLOCKS(&(mp->m_sb));

XFS_MAX_DBLOCKS is the maximum number of blocks that the given
geometry could support.  But the last AG could be shorter than the
others.  I think you really want to check against mp->m_sb.sb_dblocks.

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