Commit 149fc787 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Linus Torvalds

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

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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0aa41cae
...@@ -140,7 +140,8 @@ static inline bool in_vfork(struct task_struct *tsk) ...@@ -140,7 +140,8 @@ static inline bool in_vfork(struct task_struct *tsk)
* another oom-unkillable task does this it should blame itself. * another oom-unkillable task does this it should blame itself.
*/ */
rcu_read_lock(); 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(); rcu_read_unlock();
return ret; return ret;
......
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