Re: [PATCH v2 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry()

[Joseph Qi]

On 5/17/24 5:41 PM, Ferry Meng wrote:
> Add a paranoia check to make sure it doesn't stray beyond valid memory
> region containing ocfs2 xattr entries when scanning for a match.
> It will prevent out-of-bound access in case of crafted images.
> 
> Signed-off-by: Ferry Meng <mengferry@xxxxxxxxxxxxxxxxx>

Reported-by: lei lu <llfamsec@xxxxxxxxx>
Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>

> ---
>  fs/ocfs2/xattr.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 3b81213ed7b8..8aea94c90739 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -1062,7 +1062,7 @@ ssize_t ocfs2_listxattr(struct dentry *dentry,
>  	return i_ret + b_ret;
>  }
>  
> -static int ocfs2_xattr_find_entry(int name_index,
> +static int ocfs2_xattr_find_entry(struct inode *inode, int name_index,
>  				  const char *name,
>  				  struct ocfs2_xattr_search *xs)
>  {
> @@ -1076,6 +1076,10 @@ static int ocfs2_xattr_find_entry(int name_index,
>  	name_len = strlen(name);
>  	entry = xs->here;
>  	for (i = 0; i < le16_to_cpu(xs->header->xh_count); i++) {
> +		if ((void *)entry >= xs->end) {
> +			ocfs2_error(inode->i_sb, "corrupted xattr entries");
> +			return -EFSCORRUPTED;
> +		}
>  		cmp = name_index - ocfs2_xattr_get_type(entry);
>  		if (!cmp)
>  			cmp = name_len - entry->xe_name_len;
> @@ -1166,7 +1170,7 @@ static int ocfs2_xattr_ibody_get(struct inode *inode,
>  	xs->base = (void *)xs->header;
>  	xs->here = xs->header->xh_entries;
>  
> -	ret = ocfs2_xattr_find_entry(name_index, name, xs);
> +	ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
>  	if (ret)
>  		return ret;
>  	size = le64_to_cpu(xs->here->xe_value_size);
> @@ -2698,7 +2702,7 @@ static int ocfs2_xattr_ibody_find(struct inode *inode,
>  
>  	/* Find the named attribute. */
>  	if (oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL) {
> -		ret = ocfs2_xattr_find_entry(name_index, name, xs);
> +		ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
>  		if (ret && ret != -ENODATA)
>  			return ret;
>  		xs->not_found = ret;
> @@ -2833,7 +2837,7 @@ static int ocfs2_xattr_block_find(struct inode *inode,
>  		xs->end = (void *)(blk_bh->b_data) + blk_bh->b_size;
>  		xs->here = xs->header->xh_entries;
>  
> -		ret = ocfs2_xattr_find_entry(name_index, name, xs);
> +		ret = ocfs2_xattr_find_entry(inode, name_index, name, xs);
>  	} else
>  		ret = ocfs2_xattr_index_block_find(inode, blk_bh,
>  						   name_index,