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Subject[PATCH 3.10 22/22] sched/autogroup: Fix race with task_groups list
3.10-stable review patch.  If anyone has any objections, please let me know.


From: Gerald Schaefer <>

commit 41261b6a832ea0e788627f6a8707854423f9ff49 upstream.

In autogroup_create(), a tg is allocated and added to the task_groups
list. If CONFIG_RT_GROUP_SCHED is set, this tg is then modified while on
the list, without locking. This can race with someone walking the list,
like __enable_runtime() during CPU unplug, and result in a use-after-free

To fix this, move sched_online_group(), which adds the tg to the list,
to the end of the autogroup_create() function after the modification.

Signed-off-by: Gerald Schaefer <>
Signed-off-by: Peter Zijlstra <>
Signed-off-by: Ingo Molnar <>
Signed-off-by: Preeti U Murthy <>
Signed-off-by: Greg Kroah-Hartman <>

kernel/sched/auto_group.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -77,8 +77,6 @@ static inline struct autogroup *autogrou
if (IS_ERR(tg))
goto out_free;

- sched_online_group(tg, &root_task_group);
ag->id = atomic_inc_return(&autogroup_seq_nr);
@@ -98,6 +96,7 @@ static inline struct autogroup *autogrou
tg->autogroup = ag;

+ sched_online_group(tg, &root_task_group);
return ag;


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