Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 25/30] cgroup: fix exit() vs rmdir() race | Date | Fri, 1 Mar 2013 11:45:46 -0800 |
| |
3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Li Zefan <lizefan@huawei.com>
commit 71b5707e119653039e6e95213f00479668c79b75 upstream.
In cgroup_exit() put_css_set_taskexit() is called without any lock, which might lead to accessing a freed cgroup:
thread1 thread2 --------------------------------------------- exit() cgroup_exit() put_css_set_taskexit() atomic_dec(cgrp->count); rmdir(); /* not safe !! */ check_for_release(cgrp);
rcu_read_lock() can be used to make sure the cgroup is alive.
Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/cgroup.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -359,12 +359,20 @@ static void __put_css_set(struct css_set struct cgroup *cgrp = link->cgrp; list_del(&link->cg_link_list); list_del(&link->cgrp_link_list); + + /* + * We may not be holding cgroup_mutex, and if cgrp->count is + * dropped to 0 the cgroup can be destroyed at any time, hence + * rcu_read_lock is used to keep it alive. + */ + rcu_read_lock(); if (atomic_dec_and_test(&cgrp->count) && notify_on_release(cgrp)) { if (taskexit) set_bit(CGRP_RELEASABLE, &cgrp->flags); check_for_release(cgrp); } + rcu_read_unlock(); kfree(link); }
| |