From: mjg <mjg@FreeBSD.org>
Date: Tue, 17 Sep 2019 08:09:39 +0000 (+0000)
Subject: vfs: fix braino resulting in NULL pointer deref in r352424
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=9757eca049e7f919be04b3dc36c3c4e23e69876a;p=freebsd.git

vfs: fix braino resulting in NULL pointer deref in r352424

The breakage was added after all the testing and the testing which followed
was not sufficient to find it.

Reported by:	pho
Sponsored by:	The FreeBSD Foundation
---

diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index 163a617a3ec..2fd95fbc8b4 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -613,11 +613,13 @@ vop_stdgetwritemount(ap)
 		vfs_op_thread_exit(mp);
 	} else {
 		MNT_ILOCK(mp);
-		if (mp == vp->v_mount)
+		if (mp == vp->v_mount) {
 			MNT_REF(mp);
-		else
+			MNT_IUNLOCK(mp);
+		} else {
+			MNT_IUNLOCK(mp);
 			mp = NULL;
-		MNT_IUNLOCK(mp);
+		}
 	}
 	*(ap->a_mpp) = mp;
 	return (0);