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Commit ccdb5fa3 authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Greg Kroah-Hartman
Browse files

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: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1369411669-46971-2-git-send-email-gerald.schaefer@de.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarPreeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 80ae5669

kernel/sched/auto_group.c

+1 −2
Original line number Diff line number Diff line
@@ -77,8 +77,6 @@ static inline struct autogroup *autogroup_create(void) 
	if (IS_ERR(tg))

		goto out_free;



	sched_online_group(tg, &root_task_group);



	kref_init(&ag->kref);

	init_rwsem(&ag->lock);

	ag->id = atomic_inc_return(&autogroup_seq_nr);
@@ -98,6 +96,7 @@ static inline struct autogroup *autogroup_create(void) 
#endif

	tg->autogroup = ag;



	sched_online_group(tg, &root_task_group);

	return ag;



out_free: