ksmbd: fix bug on trap in smb2_lock

BugLink: https://bugs.launchpad.net/bugs/2107437

commit e26e2d2 upstream.

If lock count is greater than 1, flags could be old value.
It should be checked with flags of smb_lock, not flags.
It will cause bug-on trap from locks_free_lock in error handling
routine.

Cc: stable@vger.kernel.org
Reported-by: Norbert Szetei <norbert@doyensec.com>
Tested-by: Norbert Szetei <norbert@doyensec.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: namjaejeon

fs/smb/server/smb2pdu.c

@@ -7455,7 +7455,7 @@ int smb2_lock(struct ksmbd_work *work)
 retry:
 		rc = vfs_lock_file(filp, smb_lock->cmd, flock, NULL);
 skip:
-		if (flags & SMB2_LOCKFLAG_UNLOCK) {
+		if (smb_lock->flags & SMB2_LOCKFLAG_UNLOCK) {
 			if (!rc) {
 				ksmbd_debug(SMB, "File unlocked\n");
 			} else if (rc == -ENOENT) {