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authorMatthew Wilcox (Oracle) <willy@infradead.org>2021-03-12 21:08:03 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-03-13 11:27:30 -0800
commit149fc787353f65b7e72e05e7b75d34863266c3e2 (patch)
tree9c1436d6fd11b3ba6e8151c707f11b8c5cfe788e
parent0aa41cae92c1e2e61ae5b3a2dde8e674172e40ac (diff)
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: b18dc5f291c0 ("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>
-rw-r--r--include/linux/sched/mm.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 1ae08b8462a4..90b2a0bce11c 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -140,7 +140,8 @@ 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;

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