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Date:      Fri, 13 Oct 2017 09:42:05 +0000 (UTC)
From:      Andriy Gapon <avg@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r324591 - head/sys/kern
Message-ID:  <201710130942.v9D9g5oS014351@repo.freebsd.org>
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Author: avg
Date: Fri Oct 13 09:42:05 2017
New Revision: 324591
URL: https://svnweb.freebsd.org/changeset/base/324591

Log:
  remove process and jail directory machinations from dounmount
  
  The manipulations done by mountcheckdirs() are not that useful during
  the unmount, they can bring about unexpected security consequences.
  
  Thic change effectively reverts the change in r73241.
  
  The change also allows to simplify the handling of rootvnode global
  variable.
  
  Discussed with:	mckusick, mjg, kib
  Reviewed by:	trasz
  MFC after:	1 month
  Differential Revision: https://reviews.freebsd.org/D12366

Modified:
  head/sys/kern/vfs_mount.c

Modified: head/sys/kern/vfs_mount.c
==============================================================================
--- head/sys/kern/vfs_mount.c	Fri Oct 13 09:21:41 2017	(r324590)
+++ head/sys/kern/vfs_mount.c	Fri Oct 13 09:42:05 2017	(r324591)
@@ -1262,7 +1262,7 @@ dounmount_cleanup(struct mount *mp, struct vnode *cove
 int
 dounmount(struct mount *mp, int flags, struct thread *td)
 {
-	struct vnode *coveredvp, *fsrootvp;
+	struct vnode *coveredvp;
 	int error;
 	uint64_t async_flag;
 	int mnt_gen_r;
@@ -1364,22 +1364,6 @@ dounmount(struct mount *mp, int flags, struct thread *
 	MNT_IUNLOCK(mp);
 	cache_purgevfs(mp, false); /* remove cache entries for this file sys */
 	vfs_deallocate_syncvnode(mp);
-	/*
-	 * For forced unmounts, move process cdir/rdir refs on the fs root
-	 * vnode to the covered vnode.  For non-forced unmounts we want
-	 * such references to cause an EBUSY error.
-	 */
-	if ((flags & MNT_FORCE) &&
-	    VFS_ROOT(mp, LK_EXCLUSIVE, &fsrootvp) == 0) {
-		if (mp->mnt_vnodecovered != NULL &&
-		    (mp->mnt_flag & MNT_IGNORE) == 0)
-			mountcheckdirs(fsrootvp, mp->mnt_vnodecovered);
-		if (fsrootvp == rootvnode) {
-			vrele(rootvnode);
-			rootvnode = NULL;
-		}
-		vput(fsrootvp);
-	}
 	if ((mp->mnt_flag & MNT_RDONLY) != 0 || (flags & MNT_FORCE) != 0 ||
 	    (error = VFS_SYNC(mp, MNT_WAIT)) == 0)
 		error = VFS_UNMOUNT(mp, flags);
@@ -1391,17 +1375,6 @@ dounmount(struct mount *mp, int flags, struct thread *
 	 * it doesn't exist anymore.
 	 */
 	if (error && error != ENXIO) {
-		if ((flags & MNT_FORCE) &&
-		    VFS_ROOT(mp, LK_EXCLUSIVE, &fsrootvp) == 0) {
-			if (mp->mnt_vnodecovered != NULL &&
-			    (mp->mnt_flag & MNT_IGNORE) == 0)
-				mountcheckdirs(mp->mnt_vnodecovered, fsrootvp);
-			if (rootvnode == NULL) {
-				rootvnode = fsrootvp;
-				vref(rootvnode);
-			}
-			vput(fsrootvp);
-		}
 		MNT_ILOCK(mp);
 		mp->mnt_kern_flag &= ~MNTK_NOINSMNTQ;
 		if ((mp->mnt_flag & MNT_RDONLY) == 0) {
@@ -1432,6 +1405,10 @@ dounmount(struct mount *mp, int flags, struct thread *
 		VOP_UNLOCK(coveredvp, 0);
 	}
 	vfs_event_signal(NULL, VQ_UNMOUNT, 0);
+	if (rootvnode != NULL && mp == rootvnode->v_mount) {
+		vrele(rootvnode);
+		rootvnode = NULL;
+	}
 	if (mp == rootdevmp)
 		rootdevmp = NULL;
 	vfs_mount_destroy(mp);

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