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Re: [patch] xfs: check for underflow in xfs_iformat_fork()

To: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Subject: Re: [patch] xfs: check for underflow in xfs_iformat_fork()
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Thu, 15 Aug 2013 18:10:43 +0800
Cc: Ben Myers <bpm@xxxxxxx>, Alex Elder <elder@xxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, kernel-janitors@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130815055338.GC23580@xxxxxxxxxxxxxx>
References: <20130815055338.GC23580@xxxxxxxxxxxxxx>
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On 08/15/2013 01:53 PM, Dan Carpenter wrote:

> The "di_size" variable comes from the disk and it's a signed 64 bit.
> We check the upper limit but we should check for negative numbers as
> well.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> 
> diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> index 123971b..849fc70 100644
> --- a/fs/xfs/xfs_inode_fork.c
> +++ b/fs/xfs/xfs_inode_fork.c
> @@ -167,7 +167,8 @@ xfs_iformat_fork(
>                       }
>  
>                       di_size = be64_to_cpu(dip->di_size);
> -                     if (unlikely(di_size > XFS_DFORK_DSIZE(dip, 
> ip->i_mount))) {
> +                     if (unlikely(di_size < 0 ||

But the di_size is initialized to ZERO while allocating a new inode on disk.
I wonder if that is better to ASSERT in this case because the current check
is used to make sure that the item is inlined, or we don't need it at all.

> +                                  di_size > XFS_DFORK_DSIZE(dip, 
> ip->i_mount))) {
>                               xfs_warn(ip->i_mount,
>                       "corrupt inode %Lu (bad size %Ld for local inode).",
>                                       (unsigned long long) ip->i_ino,
>

Thanks,
-Jeff

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