linux-kernel - Re: [PATCH v2 2/2] ocfs2: strict bound check before memcmp in ocfs2_xattr_find

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Message-ID: <784b6bcc-067a-4a27-93e9-60e96da2befb@linux.alibaba.com>
Date: Fri, 17 May 2024 18:53:27 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Ferry Meng <mengferry@...ux.alibaba.com>, lei lu <llfamsec@...il.com>,
 akpm <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Mark Fasheh <mark@...heh.com>,
 Joel Becker <jlbec@...lplan.org>, ocfs2-devel@...ts.linux.dev
Subject: Re: [PATCH v2 2/2] ocfs2: strict bound check before memcmp in
 ocfs2_xattr_find_entry()



On 5/17/24 5:41 PM, Ferry Meng wrote:
> xattr in ocfs2 maybe 'non-indexed', which 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 crafted poisonous
> images.
> 
> Signed-off-by: Ferry Meng <mengferry@...ux.alibaba.com>

Reported-by: lei lu <llfamsec@...il.com>
Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>

> ---
>  fs/ocfs2/xattr.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 8aea94c90739..35c0cc2a51af 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -1068,7 +1068,7 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
>  {
>  	struct ocfs2_xattr_entry *entry;
>  	size_t name_len;
> -	int i, cmp = 1;
> +	int i, name_offset, cmp = 1;
>  
>  	if (name == NULL)
>  		return -EINVAL;
> @@ -1083,10 +1083,15 @@ static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
>  		cmp = name_index - ocfs2_xattr_get_type(entry);
>  		if (!cmp)
>  			cmp = name_len - entry->xe_name_len;
> -		if (!cmp)
> -			cmp = memcmp(name, (xs->base +
> -				     le16_to_cpu(entry->xe_name_offset)),
> -				     name_len);
> +		if (!cmp) {
> +			name_offset = le16_to_cpu(entry->xe_name_offset);
> +			if ((xs->base + name_offset + name_len) > xs->end) {
> +				ocfs2_error(inode->i_sb,
> +					    "corrupted xattr entries");
> +				return -EFSCORRUPTED;
> +			}
> +			cmp = memcmp(name, (xs->base + name_offset), name_len);
> +		}
>  		if (cmp == 0)
>  			break;
>  		entry += 1;