tlb_gather_mmu(&tlb, mm, 0, -1) means gathering all virtual memory space.
In this case, tlb->fullmm is true. Some archs like arm64 doesn't flush
TLB when tlb->fullmm is true:
commit 5a7862e83000 ("arm64: tlbflush: avoid flushing when fullmm == 1").
Which makes leaking of tlb entries. For example, when oom_reaper
selects a task and reaps its virtual memory space, another thread
in this task group may still running on another core and access
these already freed memory through tlb entries.
This patch gather each vma instead of gathering full vm space,
tlb->fullmm is not true. The behavior of oom reaper become similar
to munmapping before do_exit, which should be safe for all archs.
Signed-off-by: Wang Nan <[email protected]>
Cc: Bob Liu <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
---
mm/oom_kill.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index dee0f75..18c5b35 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -532,7 +532,6 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
*/
set_bit(MMF_UNSTABLE, &mm->flags);
- tlb_gather_mmu(&tlb, mm, 0, -1);
for (vma = mm->mmap ; vma; vma = vma->vm_next) {
if (!can_madv_dontneed_vma(vma))
continue;
@@ -547,11 +546,13 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
* we do not want to block exit_mmap by keeping mm ref
* count elevated without a good reason.
*/
- if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED))
+ if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
+ tlb_gather_mmu(&tlb, mm, vma->vm_start, vma->vm_end);
unmap_page_range(&tlb, vma, vma->vm_start, vma->vm_end,
NULL);
+ tlb_finish_mmu(&tlb, vma->vm_start, vma->vm_end);
+ }
}
- tlb_finish_mmu(&tlb, 0, -1);
pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
task_pid_nr(tsk), tsk->comm,
K(get_mm_counter(mm, MM_ANONPAGES)),
--
2.10.1
From 1583389783059530692@xxx Tue Nov 07 07:02:48 +0000 2017
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