sched/autogroup: Fix race with task_groups list
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 bug. 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 <gerald.schaefer@de.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1369411669-46971-2-git-send-email-gerald.schaefer@de.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -77,8 +77,6 @@ static inline struct autogroup *autogroup_create(void)
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if (IS_ERR(tg))
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goto out_free;
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sched_online_group(tg, &root_task_group);
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kref_init(&ag->kref);
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init_rwsem(&ag->lock);
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ag->id = atomic_inc_return(&autogroup_seq_nr);
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@ -98,6 +96,7 @@ static inline struct autogroup *autogroup_create(void)
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#endif
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tg->autogroup = ag;
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sched_online_group(tg, &root_task_group);
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return ag;
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out_free:
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