diff options
| author | Li Zefan <lizefan@huawei.com> | 2013-01-24 14:43:28 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-03-04 06:09:07 +0800 |
| commit | cc0e3e13b0a90e5ff42d5b134939eacf5e7e497c (patch) | |
| tree | 9c755b28f50082b772b96ee2b14514f977f8f031 | |
| parent | 6403d47ff9392807fcfa4464527193e0cab65b2a (diff) | |
cgroup: fix exit() vs rmdir() race
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>
| -rw-r--r-- | kernel/cgroup.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1749dcd976b..b964f9e406f 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -359,12 +359,20 @@ static void __put_css_set(struct css_set *cg, int taskexit) 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); } |