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SubjectRe: [PATCH 1/2] ocfs2: add bounds checking to ocfs2_xattr_find_entry()
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On 5/15/24 9:29 PM, Ferry Meng wrote:
> Just add redundant (perhaps paranoia) checks to make sure it doesn't
> stray beyond valid meory region of ocfs2 xattr entry array during a
> single match.
>
> Maybe this patch can prevent some crash caused by crafted poison images.
>

I'd rather restructure the commit message as below:

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@linux.alibaba.com>
> ---
> fs/ocfs2/xattr.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index 3b81213ed7b8..37be4a286faf 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -1062,8 +1062,8 @@ ssize_t ocfs2_listxattr(struct dentry *dentry,
> return i_ret + b_ret;
> }
>
> -static int ocfs2_xattr_find_entry(int name_index,
> - const char *name,
> +static int ocfs2_xattr_find_entry(struct inode *inode, void *end,

'end' can be obtained from ocfs2_xattr_search directly.

Thanks,
Joseph

> + int name_index, const char *name,
> struct ocfs2_xattr_search *xs)
> {
> struct ocfs2_xattr_entry *entry;
> @@ -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 >= 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, xs->end, 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, xs->end, 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, xs->end, name_index, name, xs);
> } else
> ret = ocfs2_xattr_index_block_find(inode, blk_bh,
> name_index,

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