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| author | Li Zefan <lizf@cn.fujitsu.com> | 2010-04-22 17:29:24 +0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-05-04 09:24:59 -0700 |
| commit | 9a9686b634acc5cb6b7c601c171ae64af0318a24 (patch) | |
| tree | 4a8431117018d8883c6d34d5c06f2eff99dcfed6 /kernel/cgroup.c | |
| parent | e35ec2d2c1fc45dd3e46dde74bb0c4c4366125bf (diff) | |
| download | lwn-9a9686b634acc5cb6b7c601c171ae64af0318a24.tar.gz lwn-9a9686b634acc5cb6b7c601c171ae64af0318a24.zip | |
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.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index e2769e13980c..4ca928db890c 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) |