[PATCH 1/3] cgroup: fix locking in cgroupstats_build()

[PATCH 1/3] cgroup: fix locking in cgroupstats_build()

[Li Zefan]

css_set_lock has been converted to css_set_rwsem, and rwsem can't
nested inside rcu_read_lock.

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
 kernel/cgroup.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index af4ecc3..0e794ca 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2997,6 +2997,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
 	    kernfs_type(kn) != KERNFS_DIR)
 		return -EINVAL;
 
+	mutex_lock(&cgroup_mutex);
+
 	/*
 	 * We aren't being called from kernfs and there's no guarantee on
 	 * @kn->priv's validity.  For this and css_tryget_from_dir(),
@@ -3004,10 +3006,12 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
 	 */
 	rcu_read_lock();
 	cgrp = rcu_dereference(kn->priv);
-	if (!cgrp) {
+	if (!cgrp || cgroup_is_dead(cgrp)) {
 		rcu_read_unlock();
+		mutex_unlock(&cgroup_mutex);
 		return -ENOENT;
 	}
+	rcu_read_unlock();
 
 	css_task_iter_start(&cgrp->dummy_css, &it);
 	while ((tsk = css_task_iter_next(&it))) {
@@ -3032,7 +3036,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
 	}
 	css_task_iter_end(&it);
 
-	rcu_read_unlock();
+	mutex_unlock(&cgroup_mutex);
 	return 0;
 }
 
-- 
1.8.0.2

[PATCH 2/3] cgroup: fix memory leak in cgroup_mount()

[Li Zefan]

We should free the memory allocated in parse_cgroupfs_options() before
calling this function again.

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
 kernel/cgroup.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0e794ca..37d94a2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1540,6 +1540,8 @@ retry:
 		if (!atomic_inc_not_zero(&root->top_cgroup.refcnt)) {
 			mutex_unlock(&cgroup_mutex);
 			mutex_unlock(&cgroup_tree_mutex);
+			kfree(opts.release_agent);
+			kfree(opts.name);
 			msleep(10);
 			goto retry;
 		}
-- 
1.8.0.2

[PATCH 3/3] cgroup: deal with dummp_top in cgroup_name() and cgroup_path()

[Li Zefan]

My kernel fails to boot, because blkcg calls cgroup_path() while
cgroupfs is not mounted.

Fix both cgroup_name() and cgroup_path().

Signed-off-by: Li Zefan <lizefan@huawei.com>
---
 include/linux/cgroup.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ef0b3af..8c283a9 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -487,13 +487,21 @@ struct cgroup_subsys_state *seq_css(struct seq_file *seq);
 
 static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
 {
-	return kernfs_name(cgrp->kn, buf, buflen);
+	/* dummy_top doesn't have a kn associated */
+	if (cgrp->kn)
+		return kernfs_name(cgrp->kn, buf, buflen);
+	else
+		return strlcpy(buf, "/", buflen);
 }
 
 static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
 					      size_t buflen)
 {
-	return kernfs_path(cgrp->kn, buf, buflen);
+	/* dummy_top doesn't have a kn associated */
+	if (cgrp->kn)
+		return kernfs_path(cgrp->kn, buf, buflen);
+	strlcpy(buf, "/", buflen);
+	return (buflen <= 2) ? NULL : buf;
 }
 
 static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
-- 
1.8.0.2

Re: [PATCH 1/3] cgroup: fix locking in cgroupstats_build()

[Tejun Heo]

On Fri, Feb 14, 2014 at 04:54:28PM +0800, Li Zefan wrote:
> css_set_lock has been converted to css_set_rwsem, and rwsem can't
> nested inside rcu_read_lock.
> 
> Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>

Applied 1-3 to cgroup/for-3.15.

Thanks!

-- 
tejun