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Fix a couple of problems with checkdirs(): 

- vnode and cwd locks were being taken with proc_lock held, which is bad
  because proc_lock can only be held for a short period of time.

- Processes could have continually forked and escaped notice, keeping
  a reference to the old directory on top of which a new mount exists.
This commit is contained in:
ad 2008-05-06 12:51:22 +00:00
parent bdaf7ef5fc
commit 8384d709ae
1 changed files with 48 additions and 24 deletions
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72
sys/kern/vfs_syscalls.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: vfs_syscalls.c,v 1.354 2008/04/30 12:49:17 ad Exp $ */
/* $NetBSD: vfs_syscalls.c,v 1.355 2008/05/06 12:51:22 ad Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@ -63,7 +63,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_syscalls.c,v 1.354 2008/04/30 12:49:17 ad Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_syscalls.c,v 1.355 2008/05/06 12:51:22 ad Exp $");
#include "opt_compat_netbsd.h"
#include "opt_compat_43.h"
@ -561,35 +561,59 @@ void
checkdirs(struct vnode *olddp)
{
struct cwdinfo *cwdi;
struct vnode *newdp;
struct vnode *newdp, *rele1, *rele2;
struct proc *p;
bool retry;
if (olddp->v_usecount == 1)
return;
if (VFS_ROOT(olddp->v_mountedhere, &newdp))
panic("mount: lost mount");
mutex_enter(proc_lock);
/* XXXAD Should not be acquiring these locks with proc_lock held!! */
PROCLIST_FOREACH(p, &allproc) {
if ((p->p_flag & PK_MARKER) != 0)
continue;
cwdi = p->p_cwdi;
if (!cwdi)
continue;
rw_enter(&cwdi->cwdi_lock, RW_WRITER);
if (cwdi->cwdi_cdir == olddp) {
vrele(cwdi->cwdi_cdir);
VREF(newdp);
cwdi->cwdi_cdir = newdp;
do {
retry = false;
mutex_enter(proc_lock);
PROCLIST_FOREACH(p, &allproc) {
if ((p->p_flag & PK_MARKER) != 0)
continue;
if ((cwdi = p->p_cwdi) == NULL)
continue;
/*
* Can't change to the old directory any more,
* so even if we see a stale value it's not a
* problem.
*/
if (cwdi->cwdi_cdir != olddp &&
cwdi->cwdi_rdir != olddp)
continue;
retry = true;
rele1 = NULL;
rele2 = NULL;
atomic_inc_uint(&cwdi->cwdi_refcnt);
mutex_exit(proc_lock);
rw_enter(&cwdi->cwdi_lock, RW_WRITER);
if (cwdi->cwdi_cdir == olddp) {
rele1 = cwdi->cwdi_cdir;
VREF(newdp);
cwdi->cwdi_cdir = newdp;
}
if (cwdi->cwdi_rdir == olddp) {
rele2 = cwdi->cwdi_rdir;
VREF(newdp);
cwdi->cwdi_rdir = newdp;
}
rw_exit(&cwdi->cwdi_lock);
cwdfree(cwdi);
if (rele1 != NULL)
vrele(rele1);
if (rele2 != NULL)
vrele(rele2);
mutex_enter(proc_lock);
break;
}
if (cwdi->cwdi_rdir == olddp) {
vrele(cwdi->cwdi_rdir);
VREF(newdp);
cwdi->cwdi_rdir = newdp;
}
rw_exit(&cwdi->cwdi_lock);
}
mutex_exit(proc_lock);
mutex_exit(proc_lock);
} while (retry);
if (rootvnode == olddp) {
vrele(rootvnode);
VREF(newdp);