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Dounmount() violates the locking protocol for member v_mountedhere.

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A vnode lock is required to access or modify this field.

Lock/unlock the vnode when clearing v_mountedhere.

Reviewed by: David Holland <dholland@netbsd.org>

Should fix PR #48135 (Bad locking for umount)
This commit is contained in:
hannken 2013-08-30 12:58:22 +00:00
parent 1f2f41bbc5
commit 1f6a95ec03
1 changed files with 7 additions and 4 deletions
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11
sys/kern/vfs_mount.c
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@ -1,4 +1,4 @@
/* $NetBSD: vfs_mount.c,v 1.19 2013/04/28 21:34:31 mlelstv Exp $ */
/* $NetBSD: vfs_mount.c,v 1.20 2013/08/30 12:58:22 hannken Exp $ */
/*-
* Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@ -67,7 +67,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.19 2013/04/28 21:34:31 mlelstv Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.20 2013/08/30 12:58:22 hannken Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@ -878,9 +878,12 @@ dounmount(struct mount *mp, int flags, struct lwp *l)
mp->mnt_iflag |= IMNT_GONE;
mutex_exit(&mp->mnt_unmounting);
mutex_enter(&mountlist_lock);
if ((coveredvp = mp->mnt_vnodecovered) != NULLVP)
if ((coveredvp = mp->mnt_vnodecovered) != NULLVP) {
vn_lock(coveredvp, LK_EXCLUSIVE | LK_RETRY);
coveredvp->v_mountedhere = NULL;
VOP_UNLOCK(coveredvp);
}
mutex_enter(&mountlist_lock);
CIRCLEQ_REMOVE(&mountlist, mp, mnt_list);
mutex_exit(&mountlist_lock);
if (TAILQ_FIRST(&mp->mnt_vnodelist) != NULL)