On Mon, Nov 6, 2017 at 11:36 AM, Wang Nan <wangnan0@xxxxxxxxxx> wrote: > 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"). > CC'ed Will Deacon. > 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 <wangnan0@xxxxxxxxxx> > Cc: Bob Liu <liubo95@xxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Roman Gushchin <guro@xxxxxx> > Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > --- > 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)), -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>