cifs: fix leak in FSCTL_ENUM_SNAPS response handling

commit 0e5c7955 upstream.

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: 834170c8 ("Enable previous version support")
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/cifs/smb2ops.c

@@ -924,6 +924,7 @@ 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;
 		}