* [PATCH 1/2] cgroup: fix exit() vsrmdir() race
@ 2013-01-24 6:43 ` Li Zefan
0 siblings, 0 replies; 10+ messages in thread
From: Li Zefan @ 2013-01-24 6:43 UTC (permalink / raw)
To: Tejun Heo; +Cc: cgroups, LKML
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-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
kernel/cgroup.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 368cff1..09c5869 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -422,12 +422,20 @@ 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);
}
--
1.8.0.2
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH 1/2] cgroup: fix exit() vsrmdir() race
@ 2013-01-24 6:43 ` Li Zefan
0 siblings, 0 replies; 10+ messages in thread
From: Li Zefan @ 2013-01-24 6:43 UTC (permalink / raw)
To: Tejun Heo; +Cc: cgroups, LKML
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>
---
kernel/cgroup.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 368cff1..09c5869 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -422,12 +422,20 @@ 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);
}
--
1.8.0.2
^ permalink raw reply related [flat|nested] 10+ messages in thread[parent not found: <5100D810.5020406-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]
* [PATCH 2/2] cgroup: remove a NULL check in cgroup_exit()
2013-01-24 6:43 ` Li Zefan
@ 2013-01-24 6:43 ` Li Zefan
-1 siblings, 0 replies; 10+ messages in thread
From: Li Zefan @ 2013-01-24 6:43 UTC (permalink / raw)
To: Tejun Heo; +Cc: cgroups, LKML
init_task.cgroups is initialized at boot phase, and whenver a ask
is forked, it's cgroups pointer is inherited from its parent, and
it's never set to NULL afterwards.
Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
kernel/cgroup.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 09c5869..5d4c92e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5011,8 +5011,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
}
task_unlock(tsk);
- if (cg)
- put_css_set_taskexit(cg);
+ put_css_set_taskexit(cg);
}
/**
--
1.8.0.2
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH 2/2] cgroup: remove a NULL check in cgroup_exit()
@ 2013-01-24 6:43 ` Li Zefan
0 siblings, 0 replies; 10+ messages in thread
From: Li Zefan @ 2013-01-24 6:43 UTC (permalink / raw)
To: Tejun Heo; +Cc: cgroups, LKML
init_task.cgroups is initialized at boot phase, and whenver a ask
is forked, it's cgroups pointer is inherited from its parent, and
it's never set to NULL afterwards.
Signed-off-by: Li Zefan <lizefan@huawei.com>
---
kernel/cgroup.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 09c5869..5d4c92e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5011,8 +5011,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
}
task_unlock(tsk);
- if (cg)
- put_css_set_taskexit(cg);
+ put_css_set_taskexit(cg);
}
/**
--
1.8.0.2
^ permalink raw reply related [flat|nested] 10+ messages in thread
[parent not found: <5100D827.20807-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]
* Re: [PATCH 2/2] cgroup: remove a NULL check in cgroup_exit()
2013-01-24 6:43 ` Li Zefan
@ 2013-01-24 18:20 ` Tejun Heo
-1 siblings, 0 replies; 10+ messages in thread
From: Tejun Heo @ 2013-01-24 18:20 UTC (permalink / raw)
To: Li Zefan; +Cc: cgroups, LKML
On Thu, Jan 24, 2013 at 02:43:51PM +0800, Li Zefan wrote:
> init_task.cgroups is initialized at boot phase, and whenver a ask
> is forked, it's cgroups pointer is inherited from its parent, and
> it's never set to NULL afterwards.
>
> Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Applied to cgroup/for-3.9.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 2/2] cgroup: remove a NULL check in cgroup_exit()
@ 2013-01-24 18:20 ` Tejun Heo
0 siblings, 0 replies; 10+ messages in thread
From: Tejun Heo @ 2013-01-24 18:20 UTC (permalink / raw)
To: Li Zefan; +Cc: cgroups, LKML
On Thu, Jan 24, 2013 at 02:43:51PM +0800, Li Zefan wrote:
> init_task.cgroups is initialized at boot phase, and whenver a ask
> is forked, it's cgroups pointer is inherited from its parent, and
> it's never set to NULL afterwards.
>
> Signed-off-by: Li Zefan <lizefan@huawei.com>
Applied to cgroup/for-3.9.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] cgroup: fix exit() vsrmdir() race
2013-01-24 6:43 ` Li Zefan
@ 2013-01-24 18:19 ` Tejun Heo
-1 siblings, 0 replies; 10+ messages in thread
From: Tejun Heo @ 2013-01-24 18:19 UTC (permalink / raw)
To: Li Zefan; +Cc: cgroups, LKML
On Thu, Jan 24, 2013 at 02:43:28PM +0800, Li Zefan wrote:
> 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-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Applying to cgroup/for-3.8-fixes w/ stable cc'd.
* Can you please add WARN_ON_ONCE(!rcu_read_lock_held()) in
check_for_release()?
* cgroup_release_agent() seems broken too. It's accessing cgrp after
removing it from release_list. Can you please fix it too?
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH 1/2] cgroup: fix exit() vsrmdir() race
@ 2013-01-24 18:19 ` Tejun Heo
0 siblings, 0 replies; 10+ messages in thread
From: Tejun Heo @ 2013-01-24 18:19 UTC (permalink / raw)
To: Li Zefan; +Cc: cgroups, LKML
On Thu, Jan 24, 2013 at 02:43:28PM +0800, Li Zefan wrote:
> 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>
Applying to cgroup/for-3.8-fixes w/ stable cc'd.
* Can you please add WARN_ON_ONCE(!rcu_read_lock_held()) in
check_for_release()?
* cgroup_release_agent() seems broken too. It's accessing cgrp after
removing it from release_list. Can you please fix it too?
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <20130124181923.GK2373-9pTldWuhBndy/B6EtB590w@public.gmane.org>]
* Re: [PATCH 1/2] cgroup: fix exit() vsrmdir() race
2013-01-24 18:19 ` Tejun Heo
@ 2013-01-24 18:36 ` Tejun Heo
-1 siblings, 0 replies; 10+ messages in thread
From: Tejun Heo @ 2013-01-24 18:36 UTC (permalink / raw)
To: Li Zefan; +Cc: cgroups, LKML
On Thu, Jan 24, 2013 at 10:19:23AM -0800, Tejun Heo wrote:
> * cgroup_release_agent() seems broken too. It's accessing cgrp after
> removing it from release_list. Can you please fix it too?
Oh, we should be okay as we're holding cgroup_mutex there. Please
forget about the above.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2013-01-24 18:36 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
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2013-01-24 6:43 [PATCH 1/2] cgroup: fix exit() vsrmdir() race Li Zefan
2013-01-24 6:43 ` Li Zefan
[not found] ` <5100D810.5020406-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-01-24 6:43 ` [PATCH 2/2] cgroup: remove a NULL check in cgroup_exit() Li Zefan
2013-01-24 6:43 ` Li Zefan
[not found] ` <5100D827.20807-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-01-24 18:20 ` Tejun Heo
2013-01-24 18:20 ` Tejun Heo
2013-01-24 18:19 ` [PATCH 1/2] cgroup: fix exit() vsrmdir() race Tejun Heo
2013-01-24 18:19 ` Tejun Heo
[not found] ` <20130124181923.GK2373-9pTldWuhBndy/B6EtB590w@public.gmane.org>
2013-01-24 18:36 ` Tejun Heo
2013-01-24 18:36 ` Tejun Heo
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