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| author | Tejun Heo <tj@kernel.org> | 2014-02-13 13:29:31 -0500 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2014-02-18 18:23:18 -0500 |
| commit | 532de3fc72adc2a6525c4d53c07bf81e1732083d (patch) | |
| tree | 72ee4b0fe873589f814939a3b4e60fedb1f9c6ef | |
| parent | 1a11533fbd71792e8c5d36f6763fbce8df0d231d (diff) | |
| download | linux-stable-532de3fc72adc2a6525c4d53c07bf81e1732083d.tar.gz linux-stable-532de3fc72adc2a6525c4d53c07bf81e1732083d.tar.bz2 linux-stable-532de3fc72adc2a6525c4d53c07bf81e1732083d.zip | |
cgroup: update cgroup_enable_task_cg_lists() to grab siglock
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>
Cc: stable@vger.kernel.org
| -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 68d87103b493..105f273b6f86 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2905,9 +2905,14 @@ 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, &task_css_set(p)->tasks); + spin_unlock_irq(&p->sighand->siglock); + task_unlock(p); } while_each_thread(g, p); read_unlock(&tasklist_lock); |