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authorLi Zefan <lizf@cn.fujitsu.com>2010-04-22 17:29:24 +0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-05-04 09:24:59 -0700
commit9a9686b634acc5cb6b7c601c171ae64af0318a24 (patch)
tree4a8431117018d8883c6d34d5c06f2eff99dcfed6 /kernel/cgroup.c
parente35ec2d2c1fc45dd3e46dde74bb0c4c4366125bf (diff)
cgroup: Fix an RCU warning in cgroup_path()
with CONFIG_PROVE_RCU=y, a warning can be triggered: # mount -t cgroup -o debug xxx /mnt # cat /proc/$$/cgroup ... kernel/cgroup.c:1649 invoked rcu_dereference_check() without protection! ... This is a false-positive, because cgroup_path() can be called with either rcu_read_lock() held or cgroup_mutex held. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e2769e13980..4ca928db890 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1646,7 +1646,9 @@ static inline struct cftype *__d_cft(struct dentry *dentry)
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
{
char *start;
- struct dentry *dentry = rcu_dereference(cgrp->dentry);
+ struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
+ rcu_read_lock_held() ||
+ cgroup_lock_is_held());
if (!dentry || cgrp == dummytop) {
/*
@@ -1662,13 +1664,17 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
*--start = '\0';
for (;;) {
int len = dentry->d_name.len;
+
if ((start -= len) < buf)
return -ENAMETOOLONG;
- memcpy(start, cgrp->dentry->d_name.name, len);
+ memcpy(start, dentry->d_name.name, len);
cgrp = cgrp->parent;
if (!cgrp)
break;
- dentry = rcu_dereference(cgrp->dentry);
+
+ dentry = rcu_dereference_check(cgrp->dentry,
+ rcu_read_lock_held() ||
+ cgroup_lock_is_held());
if (!cgrp->parent)
continue;
if (--start < buf)