Commit 29e28a13 authored Mar 12, 2021 by Matthew Wilcox (Oracle) Committed by Greg Kroah-Hartman Mar 17, 2021

include/linux/sched/mm.h: use rcu_dereference in in_vfork()

[ Upstream commit 149fc787353f65b7e72e05e7b75d34863266c3e2 ]

Fix a sparse warning by using rcu_dereference().  Technically this is a
bug and a sufficiently aggressive compiler could reload the `real_parent'
pointer outside the protection of the rcu lock (and access freed memory),
but I think it's pretty unlikely to happen.

Link: https://lkml.kernel.org/r/20210221194207.1351703-1-willy@infradead.org


Fixes: b18dc5f2 ("mm, oom: skip vforked tasks from being selected")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 99f1960c

include/linux/sched/mm.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -167,7 +167,8 @@ static inline bool in_vfork(struct task_struct *tsk)
		* another oom-unkillable task does this it should blame itself.
		*/
		rcu_read_lock();
		ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
		ret = tsk->vfork_done &&
		rcu_dereference(tsk->real_parent)->mm == tsk->mm;
		rcu_read_unlock();

		return ret;