ocfs2: add bounds checking to ocfs2_xattr_find_entry()

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.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ferry Meng <[email protected]>
Signed-off-by: Joseph Qi <[email protected]>
Reported-by: lei lu <[email protected]>
Reviewed-by: Joseph Qi <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Changwei Ge <[email protected]>
Cc: Gang He <[email protected]>
Cc: Jun Piao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: jdmfr

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,