The patch titled
Subject: include/linux/sched/mm.h: use rcu_dereference in in_vfork()
has been added to the -mm tree. Its filename is
mm-use-rcu_dereference-in-in_vfork.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-use-rcu_dereference-in-in_vfork.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-use-rcu_dereference-in-in_vfork.patch
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxx
Fixes: b18dc5f291c0 ("mm, oom: skip vforked tasks from being selected")
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched/mm.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/include/linux/sched/mm.h~mm-use-rcu_dereference-in-in_vfork
+++ a/include/linux/sched/mm.h
@@ -140,7 +140,8 @@ static inline bool in_vfork(struct task_
* 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;
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-use-rcu_dereference-in-in_vfork.patch
mm-filemap-use-filemap_read_page-in-filemap_fault.patch
mm-filemap-drop-check-for-truncated-page-after-i-o.patch
mm-page_alloc-rename-alloc_mask-to-alloc_gfp.patch
mm-page_alloc-rename-gfp_mask-to-gfp.patch
mm-page_alloc-combine-__alloc_pages-and-__alloc_pages_nodemask.patch
mm-mempolicy-rename-alloc_pages_current-to-alloc_pages.patch
mm-mempolicy-rewrite-alloc_pages-documentation.patch
mm-mempolicy-rewrite-alloc_pages_vma-documentation.patch
mm-mempolicy-fix-mpol_misplaced-kernel-doc.patch
