diff options
| author | Tejun Heo <tj@kernel.org> | 2014-02-13 13:29:31 -0500 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-04-02 00:58:54 +0100 |
| commit | a320419451b152ce343bd59675a5bfa0beffe9e9 (patch) | |
| tree | 60d5367474eb8fe43761063dc0564edcbd3ff06e /kernel | |
| parent | c37145e29e4cd71a5aff0e2bb5837e821d538c16 (diff) | |
cgroup: update cgroup_enable_task_cg_lists() to grab siglock
commit 532de3fc72adc2a6525c4d53c07bf81e1732083d upstream.
Currently, there's nothing preventing cgroup_enable_task_cg_lists()
from missing set PF_EXITING and race against cgroup_exit(). Depending
on the timing, cgroup_exit() may finish with the task still linked on
css_set leading to list corruption. Fix it by grabbing siglock in
cgroup_enable_task_cg_lists() so that PF_EXITING is guaranteed to be
visible.
This whole on-demand cg_list optimization is extremely fragile and has
ample possibility to lead to bugs which can cause things like
once-a-year oops during boot. I'm wondering whether the better
approach would be just adding "cgroup_disable=all" handling which
disables the whole cgroup rather than tempting fate with this
on-demand craziness.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 2a1ffb7b191..93fc15e6ddc 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2785,9 +2785,14 @@ static void cgroup_enable_task_cg_lists(void) * We should check if the process is exiting, otherwise * it will race with cgroup_exit() in that the list * entry won't be deleted though the process has exited. + * Do it while holding siglock so that we don't end up + * racing against cgroup_exit(). */ + spin_lock_irq(&p->sighand->siglock); if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list)) list_add(&p->cg_list, &p->cgroups->tasks); + spin_unlock_irq(&p->sighand->siglock); + task_unlock(p); } while_each_thread(g, p); write_unlock(&css_set_lock); |