ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()

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.

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: Changwei Ge <[email protected]>
Cc: Gang He <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Jun Piao <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Mark Fasheh <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: jdmfr

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;