path: root/block
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authorLi Zefan <lizefan@huawei.com>2013-03-01 15:01:56 +0800
committerTejun Heo <tj@kernel.org>2013-03-04 09:50:08 -0800
commit65dff759d2948cf18e2029fc5c0c595b8b7da3a5 (patch)
tree2904e81e44bb939413f406bbb2056e88df008f72 /block
parent6dbe51c251a327e012439c4772097a13df43c5b8 (diff)
cgroup: fix cgroup_path() vs rename() race
rename() will change dentry->d_name. The result of this race can be worse than seeing partially rewritten name, but we might access a stale pointer because rename() will re-allocate memory to hold a longer name. As accessing dentry->name must be protected by dentry->d_lock or parent inode's i_mutex, while on the other hand cgroup-path() can be called with some irq-safe spinlocks held, we can't generate cgroup path using dentry->d_name. Alternatively we make a copy of dentry->d_name and save it in cgrp->name when a cgroup is created, and update cgrp->name at rename(). v5: use flexible array instead of zero-size array. v4: - allocate root_cgroup_name and all root_cgroup->name points to it. - add cgroup_name() wrapper. v3: use kfree_rcu() instead of synchronize_rcu() in user-visible path. v2: make cgrp->name RCU safe. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'block')
1 files changed, 0 insertions, 2 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index f2b292925cc..4e595ee8c91 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -247,9 +247,7 @@ static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
int ret;
- rcu_read_lock();
ret = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
- rcu_read_unlock();
if (ret)
strncpy(buf, "<unavailable>", buflen);
return ret;