* [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc
@ 2011-12-15 19:36 Mandeep Singh Baines
2011-12-15 21:23 ` Tejun Heo
0 siblings, 1 reply; 4+ messages in thread
From: Mandeep Singh Baines @ 2011-12-15 19:36 UTC (permalink / raw)
To: Tejun Heo, Li Zefan, linux-kernel
Cc: Mandeep Singh Baines, Tejun Heo, Li Zefan, containers, cgroups,
stable, KAMEZAWA Hiroyuki, Frederic Weisbecker, Oleg Nesterov,
Andrew Morton, Paul Menage, Olof Johansson
There is a BUG when migrating a PF_EXITING proc. Since css_set_prefetch()
is not called for the PF_EXITING case, find_existing_css_set() will return
NULL inside cgroup_task_migrate() causing a BUG.
This bug is easy to reproduce. Create a zombie and echo its pid to
cgroup.procs.
$ cat zombie.c
\#include <unistd.h>
int main()
{
if (fork())
pause();
return 0;
}
$
We are hitting this bug pretty regularly on ChromeOS.
This bug is already fixed by Tejun Heo's cgroup patchset which is
targetted for the next merge window:
https://lkml.org/lkml/2011/11/1/356
I've create a smaller patch here which just fixes this bug so that a
fix can be merged into the current release and stable.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Downstream-Bug-Report: http://crosbug.com/23953
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: containers@lists.linux-foundation.org
Cc: cgroups@vger.kernel.org
Cc: stable@kernel.org
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Olof Johansson <olofj@chromium.org>
---
kernel/cgroup.c | 5 -----
1 files changed, 0 insertions(+), 5 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index d9d5648..a184470 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2098,11 +2098,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
continue;
/* get old css_set pointer */
task_lock(tsk);
- if (tsk->flags & PF_EXITING) {
- /* ignore this task if it's going away */
- task_unlock(tsk);
- continue;
- }
oldcg = tsk->cgroups;
get_css_set(oldcg);
task_unlock(tsk);
--
1.7.3.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc
2011-12-15 19:36 [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc Mandeep Singh Baines
@ 2011-12-15 21:23 ` Tejun Heo
2011-12-16 2:12 ` Li Zefan
0 siblings, 1 reply; 4+ messages in thread
From: Tejun Heo @ 2011-12-15 21:23 UTC (permalink / raw)
To: Mandeep Singh Baines
Cc: Li Zefan, linux-kernel, containers, cgroups, stable,
KAMEZAWA Hiroyuki, Frederic Weisbecker, Oleg Nesterov,
Andrew Morton, Paul Menage, Olof Johansson
On Thu, Dec 15, 2011 at 11:36:43AM -0800, Mandeep Singh Baines wrote:
> There is a BUG when migrating a PF_EXITING proc. Since css_set_prefetch()
> is not called for the PF_EXITING case, find_existing_css_set() will return
> NULL inside cgroup_task_migrate() causing a BUG.
>
> This bug is easy to reproduce. Create a zombie and echo its pid to
> cgroup.procs.
>
> $ cat zombie.c
> \#include <unistd.h>
>
> int main()
> {
> if (fork())
> pause();
> return 0;
> }
> $
>
> We are hitting this bug pretty regularly on ChromeOS.
>
> This bug is already fixed by Tejun Heo's cgroup patchset which is
> targetted for the next merge window:
>
> https://lkml.org/lkml/2011/11/1/356
>
> I've create a smaller patch here which just fixes this bug so that a
> fix can be merged into the current release and stable.
Looks safe to me. Li?
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc
2011-12-15 21:23 ` Tejun Heo
@ 2011-12-16 2:12 ` Li Zefan
2011-12-19 17:13 ` Tejun Heo
0 siblings, 1 reply; 4+ messages in thread
From: Li Zefan @ 2011-12-16 2:12 UTC (permalink / raw)
To: Tejun Heo
Cc: Mandeep Singh Baines, linux-kernel, containers, cgroups, stable,
KAMEZAWA Hiroyuki, Frederic Weisbecker, Oleg Nesterov,
Andrew Morton, Paul Menage, Olof Johansson
Tejun Heo wrote:
> On Thu, Dec 15, 2011 at 11:36:43AM -0800, Mandeep Singh Baines wrote:
>> There is a BUG when migrating a PF_EXITING proc. Since css_set_prefetch()
>> is not called for the PF_EXITING case, find_existing_css_set() will return
>> NULL inside cgroup_task_migrate() causing a BUG.
>>
>> This bug is easy to reproduce. Create a zombie and echo its pid to
>> cgroup.procs.
>>
>> $ cat zombie.c
>> \#include <unistd.h>
>>
>> int main()
>> {
>> if (fork())
>> pause();
>> return 0;
>> }
>> $
>>
>> We are hitting this bug pretty regularly on ChromeOS.
>>
>> This bug is already fixed by Tejun Heo's cgroup patchset which is
>> targetted for the next merge window:
>>
>> https://lkml.org/lkml/2011/11/1/356
>>
>> I've create a smaller patch here which just fixes this bug so that a
>> fix can be merged into the current release and stable.
>
> Looks safe to me. Li?
>
It should be fine.
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc
2011-12-16 2:12 ` Li Zefan
@ 2011-12-19 17:13 ` Tejun Heo
0 siblings, 0 replies; 4+ messages in thread
From: Tejun Heo @ 2011-12-19 17:13 UTC (permalink / raw)
To: Li Zefan
Cc: Mandeep Singh Baines, linux-kernel, containers, cgroups, stable,
KAMEZAWA Hiroyuki, Frederic Weisbecker, Oleg Nesterov,
Andrew Morton, Paul Menage, Olof Johansson
On Fri, Dec 16, 2011 at 10:12:51AM +0800, Li Zefan wrote:
> Tejun Heo wrote:
> > On Thu, Dec 15, 2011 at 11:36:43AM -0800, Mandeep Singh Baines wrote:
> >> There is a BUG when migrating a PF_EXITING proc. Since css_set_prefetch()
> >> is not called for the PF_EXITING case, find_existing_css_set() will return
> >> NULL inside cgroup_task_migrate() causing a BUG.
> >>
> >> This bug is easy to reproduce. Create a zombie and echo its pid to
> >> cgroup.procs.
> >>
> >> $ cat zombie.c
> >> \#include <unistd.h>
> >>
> >> int main()
> >> {
> >> if (fork())
> >> pause();
> >> return 0;
> >> }
> >> $
> >>
> >> We are hitting this bug pretty regularly on ChromeOS.
> >>
> >> This bug is already fixed by Tejun Heo's cgroup patchset which is
> >> targetted for the next merge window:
> >>
> >> https://lkml.org/lkml/2011/11/1/356
> >>
> >> I've create a smaller patch here which just fixes this bug so that a
> >> fix can be merged into the current release and stable.
> >
> > Looks safe to me. Li?
> >
>
> It should be fine.
>
> Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Applied to cgroup/for-fixes-3.2. Will push to Linus in a couple of
days. It's already rc6 and a bit late tho.
Thank you.
--
tejun
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2011-12-19 17:13 UTC | newest]
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2011-12-15 19:36 [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc Mandeep Singh Baines
2011-12-15 21:23 ` Tejun Heo
2011-12-16 2:12 ` Li Zefan
2011-12-19 17:13 ` Tejun Heo
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