cifs: fix leak in FSCTL_ENUM_SNAPS response handling

The server may respond with success, and an output buffer less than
sizeof(struct smb_snapshot_array) in length. Do not leak the output
buffer in this case.

Fixes: 834170c859 ("Enable previous version support")
Signed-off-by: David Disseldorp <ddiss@suse.de>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/smb2ops.c

@@ -942,6 +942,7 @@ smb3_enum_snapshots(const unsigned int xid, struct cifs_tcon *tcon,
 		}
 		if (snapshot_in.snapshot_array_size < sizeof(struct smb_snapshot_array)) {
 			rc = -ERANGE;
+			kfree(retbuf);
 			return rc;
 		}