Module Name: src
Committed By: ad
Date: Sat May 30 18:06:17 UTC 2020
Modified Files:
src/sys/kern: vfs_cache.c
Log Message:
cache_lookup_linked():
- If the lookup fails return with the same lock held. There's no bug here
because either parent or child's lock is sufficient to prevent both from
disappearing into thin air, but may as well be correct.
- if FSCRED is passed in then skip the auth check.
To generate a diff of this commit:
cvs rdiff -u -r1.144 -r1.145 src/sys/kern/vfs_cache.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/vfs_cache.c
diff -u src/sys/kern/vfs_cache.c:1.144 src/sys/kern/vfs_cache.c:1.145
--- src/sys/kern/vfs_cache.c:1.144 Tue May 26 18:38:37 2020
+++ src/sys/kern/vfs_cache.c Sat May 30 18:06:17 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_cache.c,v 1.144 2020/05/26 18:38:37 ad Exp $ */
+/* $NetBSD: vfs_cache.c,v 1.145 2020/05/30 18:06:17 ad Exp $ */
/*-
* Copyright (c) 2008, 2019, 2020 The NetBSD Foundation, Inc.
@@ -172,7 +172,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.144 2020/05/26 18:38:37 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.145 2020/05/30 18:06:17 ad Exp $");
#define __NAMECACHE_PRIVATE
#ifdef _KERNEL_OPT
@@ -626,12 +626,10 @@ cache_lookup_linked(struct vnode *dvp, c
{
vnode_impl_t *dvi = VNODE_TO_VIMPL(dvp);
struct namecache *ncp;
+ krwlock_t *oldlock, *newlock;
uint64_t key;
int error;
- /* Establish default results. */
- *vn_ret = NULL;
-
/* If disabled, or file system doesn't support this, bail out. */
if (__predict_false((dvp->v_mount->mnt_iflag & IMNT_NCLOOKUP) == 0)) {
return false;
@@ -663,32 +661,42 @@ cache_lookup_linked(struct vnode *dvp, c
* on the lock as child -> parent is the wrong direction.
*/
if (*plock != &dvi->vi_nc_lock) {
+ oldlock = *plock;
+ newlock = &dvi->vi_nc_lock;
if (!rw_tryenter(&dvi->vi_nc_lock, RW_READER)) {
return false;
}
- if (*plock != NULL) {
- rw_exit(*plock);
+ } else {
+ oldlock = NULL;
+ newlock = NULL;
+ if (*plock == NULL) {
+ KASSERT(vrefcnt(dvp) > 0);
}
- *plock = &dvi->vi_nc_lock;
- } else if (*plock == NULL) {
- KASSERT(vrefcnt(dvp) > 0);
}
/*
* First up check if the user is allowed to look up files in this
* directory.
*/
- if (dvi->vi_nc_mode == VNOVAL) {
- return false;
- }
- KASSERT(dvi->vi_nc_uid != VNOVAL && dvi->vi_nc_gid != VNOVAL);
- error = kauth_authorize_vnode(cred, KAUTH_ACCESS_ACTION(VEXEC,
- dvp->v_type, dvi->vi_nc_mode & ALLPERMS), dvp, NULL,
- genfs_can_access(dvp, cred, dvi->vi_nc_uid, dvi->vi_nc_gid,
- dvi->vi_nc_mode & ALLPERMS, NULL, VEXEC));
- if (error != 0) {
- COUNT(ncs_denied);
- return false;
+ if (cred != FSCRED) {
+ if (dvi->vi_nc_mode == VNOVAL) {
+ if (newlock != NULL) {
+ rw_exit(newlock);
+ }
+ return false;
+ }
+ KASSERT(dvi->vi_nc_uid != VNOVAL && dvi->vi_nc_gid != VNOVAL);
+ error = kauth_authorize_vnode(cred, KAUTH_ACCESS_ACTION(VEXEC,
+ dvp->v_type, dvi->vi_nc_mode & ALLPERMS), dvp, NULL,
+ genfs_can_access(dvp, cred, dvi->vi_nc_uid, dvi->vi_nc_gid,
+ dvi->vi_nc_mode & ALLPERMS, NULL, VEXEC));
+ if (error != 0) {
+ if (newlock != NULL) {
+ rw_exit(newlock);
+ }
+ COUNT(ncs_denied);
+ return false;
+ }
}
/*
@@ -696,6 +704,9 @@ cache_lookup_linked(struct vnode *dvp, c
*/
ncp = cache_lookup_entry(dvp, name, namelen, key);
if (__predict_false(ncp == NULL)) {
+ if (newlock != NULL) {
+ rw_exit(newlock);
+ }
COUNT(ncs_miss);
SDT_PROBE(vfs, namecache, lookup, miss, dvp,
name, namelen, 0, 0);
@@ -704,11 +715,9 @@ cache_lookup_linked(struct vnode *dvp, c
if (ncp->nc_vp == NULL) {
/* found negative entry; vn is already null from above */
COUNT(ncs_neghits);
- SDT_PROBE(vfs, namecache, lookup, hit, dvp, name, namelen, 0, 0);
- return true;
+ } else {
+ COUNT(ncs_goodhits); /* XXX can be "badhits" */
}
-
- COUNT(ncs_goodhits); /* XXX can be "badhits" */
SDT_PROBE(vfs, namecache, lookup, hit, dvp, name, namelen, 0, 0);
/*
@@ -717,6 +726,12 @@ cache_lookup_linked(struct vnode *dvp, c
* looking up the next component, or the caller will release it
* manually when finished.
*/
+ if (oldlock) {
+ rw_exit(oldlock);
+ }
+ if (newlock) {
+ *plock = newlock;
+ }
*vn_ret = ncp->nc_vp;
return true;
}
