Date: Wed, 4 Feb 1998 00:33:53 +0900 (JST) From: KATO Takenori <kato@migmatite.eps.nagoya-u.ac.jp> To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: kern/5634: locking violation in umapfs Message-ID: <199802031533.AAA00403@marble.eps.nagoya-u.ac.jp>
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>Number: 5634
>Category: kern
>Synopsis: locking violation in umapfs
>Confidential: no
>Severity: critical
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Feb 3 07:40:01 PST 1998
>Last-Modified:
>Originator: KATO Takenori
>Organization:
Dept. Earth Planet. Sci, Nagoya Univ.
>Release: FreeBSD 3.0-CURRENT i386
>Environment:
umapfs kernel
>Description:
The umap_node_find() calls vget at flags = 0. This code assumes that
vget() does not lock vnode in it. It is true in 4.4BSD-Lite2 but
vget() in FreeBSD may lock vnode in it. Therefore, we should not
assume that vget() does not lock vnode.
>How-To-Repeat:
Using umapfs.
>Fix:
---------- BEGIN ----------
*** umap_subr.c.ORIG Tue Feb 3 23:12:33 1998
--- umap_subr.c Wed Feb 4 00:19:53 1998
***************
*** 143,148 ****
--- 143,150 ----
struct umap_node_hashhead *hd;
struct umap_node *a;
struct vnode *vp;
+ int error;
+ int vpunlocked;
#ifdef UMAPFS_DIAGNOSTIC
printf("umap_node_find(mp = %x, target = %x)\n", mp, targetvp);
***************
*** 165,171 ****
* stuff, but we don't want to lock
* the lower node.
*/
! if (vget(vp, 0, p)) {
#ifdef UMAPFS_DIAGNOSTIC
printf ("umap_node_find: vget failed.\n");
#endif
--- 167,181 ----
* stuff, but we don't want to lock
* the lower node.
*/
! if (VOP_ISLOCKED(vp)) {
! VOP_UNLOCK(vp, 0, p);
! vpunlocked = 1;
! } else
! vpunlocked = 0;
! error = vget(vp, 0, p);
! if (vpunlocked)
! vn_lock(vp, LK_EXCLUSIVE|LK_RETRY, p);
! if (error) {
#ifdef UMAPFS_DIAGNOSTIC
printf ("umap_node_find: vget failed.\n");
#endif
---------- END ----------
>Audit-Trail:
>Unformatted:
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