linux-kernel - Re: [PATCH 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find

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Date: Thu, 16 May 2024 09:41:58 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Ferry Meng <mengferry@...ux.alibaba.com>, Mark Fasheh <mark@...heh.com>,
 Joel Becker <jlbec@...lplan.org>, ocfs2-devel@...ts.linux.dev
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ocfs2: strict bound check before memcmp in
 ocfs2_xattr_find_entry()



On 5/15/24 9:29 PM, Ferry Meng wrote:
> xattr in ocfs2 maybe not INLINE, but saved with additional space
> requested. It's better to check if the memory is out of bound before
> memcmp, although this possibility mainly comes from custom poisonous
> images.

Specifically, this only addresses the case non-indexed xattr. 

> 
> Signed-off-by: Ferry Meng <mengferry@...ux.alibaba.com>
> ---
>  fs/ocfs2/xattr.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 37be4a286faf..4ceb0cb4cb71 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -1083,10 +1083,15 @@ static int ocfs2_xattr_find_entry(struct inode *inode, void *end,
>  		cmp = name_index - ocfs2_xattr_get_type(entry);

Or define a local variable 'offset' for le16_to_cpu(entry->xe_name_offset).

Thanks,
Joseph

>  		if (!cmp)
>  			cmp = name_len - entry->xe_name_len;
> -		if (!cmp)
> +		if (!cmp) {
> +			if ((xs->base + le16_to_cpu(entry->xe_name_offset) + name_len) > end) {
> +				ocfs2_error(inode->i_sb, "corrupted xattr entries");
> +				return -EFSCORRUPTED;
> +			}
>  			cmp = memcmp(name, (xs->base +
>  				     le16_to_cpu(entry->xe_name_offset)),
>  				     name_len);
> +		}
>  		if (cmp == 0)
>  			break;
>  		entry += 1;