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| author | Li Zefan <lizefan@huawei.com> | 2013-04-26 11:58:02 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2013-04-26 11:58:02 -0700 |
| commit | cc20e01cd607282d48f8ea538aba10fa850a4312 (patch) | |
| tree | 598ff80edab2c3bb3547dcd109e35ed1291f4454 /kernel/cgroup.c | |
| parent | 712317ad97f41e738e1a19aa0a6392a78a84094e (diff) | |
| download | lwn-cc20e01cd607282d48f8ea538aba10fa850a4312.tar.gz lwn-cc20e01cd607282d48f8ea538aba10fa850a4312.zip | |
cgroup: fix use-after-free when umounting cgroupfs
Try:
# mount -t cgroup xxx /cgroup
# mkdir /cgroup/sub && rmdir /cgroup/sub && umount /cgroup
And you might see this:
ida_remove called for id=1 which is not allocated.
It's because cgroup_kill_sb() is called to destroy root->cgroup_ida
and free cgrp->root before ida_simple_removed() is called. What's
worse is we're accessing cgrp->root while it has been freed.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 192d762ec1f4..bd4de465d5a9 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -848,9 +848,12 @@ static void cgroup_free_fn(struct work_struct *work) */ dput(cgrp->parent->dentry); + ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id); + /* * Drop the active superblock reference that we took when we - * created the cgroup + * created the cgroup. This will free cgrp->root, if we are + * holding the last reference to @sb. */ deactivate_super(cgrp->root->sb); @@ -862,7 +865,6 @@ static void cgroup_free_fn(struct work_struct *work) simple_xattrs_free(&cgrp->xattrs); - ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id); kfree(rcu_dereference_raw(cgrp->name)); kfree(cgrp); } |