* [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte
@ 2021-01-27 9:33 Miaohe Lin
2021-01-28 0:09 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Miaohe Lin @ 2021-01-27 9:33 UTC (permalink / raw)
To: akpm
Cc: mike.kravetz, shakeelb, hannes, vbabka, walken, linux-mm,
linux-kernel, linmiaohe
For PMD-mapped page (usually THP), pvmw->pte is NULL. For PTE-mapped THP,
pvmw->pte is mapped. But for HugeTLB pages, pvmw->pte is not mapped and set
to the relevant page table entry. So in page_vma_mapped_walk_done(), we may
do pte_unmap() for HugeTLB pte which is not mapped. Fix this by checking
pvmw->page against PageHuge before trying to do pte_unmap().
Fixes: commit ("ace71a19cec5 mm: introduce page_vma_mapped_walk()")
Signed-off-by: Hongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: <stable@vger.kernel.org>
---
include/linux/rmap.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 70085ca1a3fc..def5c62c93b3 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -213,7 +213,8 @@ struct page_vma_mapped_walk {
static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
{
- if (pvmw->pte)
+ /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
+ if (pvmw->pte && !PageHuge(pvmw->page))
pte_unmap(pvmw->pte);
if (pvmw->ptl)
spin_unlock(pvmw->ptl);
--
2.19.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte
2021-01-27 9:33 [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte Miaohe Lin
@ 2021-01-28 0:09 ` Andrew Morton
2021-01-28 1:54 ` Miaohe Lin
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2021-01-28 0:09 UTC (permalink / raw)
To: Miaohe Lin
Cc: mike.kravetz, shakeelb, hannes, vbabka, walken, linux-mm, linux-kernel
On Wed, 27 Jan 2021 04:33:49 -0500 Miaohe Lin <linmiaohe@huawei.com> wrote:
> For PMD-mapped page (usually THP), pvmw->pte is NULL. For PTE-mapped THP,
> pvmw->pte is mapped. But for HugeTLB pages, pvmw->pte is not mapped and set
> to the relevant page table entry. So in page_vma_mapped_walk_done(), we may
> do pte_unmap() for HugeTLB pte which is not mapped. Fix this by checking
> pvmw->page against PageHuge before trying to do pte_unmap().
>
What are the runtime consequences of this? Is there a workload which
is known to trigger it?
IOW, how do we justify a -stable backport of this fix?
>
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -213,7 +213,8 @@ struct page_vma_mapped_walk {
>
> static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
> {
> - if (pvmw->pte)
> + /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
> + if (pvmw->pte && !PageHuge(pvmw->page))
> pte_unmap(pvmw->pte);
> if (pvmw->ptl)
> spin_unlock(pvmw->ptl);
> --
> 2.19.1
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte
2021-01-28 0:09 ` Andrew Morton
@ 2021-01-28 1:54 ` Miaohe Lin
0 siblings, 0 replies; 3+ messages in thread
From: Miaohe Lin @ 2021-01-28 1:54 UTC (permalink / raw)
To: Andrew Morton
Cc: mike.kravetz, shakeelb, hannes, vbabka, walken, linux-mm, linux-kernel
Hi:
On 2021/1/28 8:09, Andrew Morton wrote:
> On Wed, 27 Jan 2021 04:33:49 -0500 Miaohe Lin <linmiaohe@huawei.com> wrote:
>
>> For PMD-mapped page (usually THP), pvmw->pte is NULL. For PTE-mapped THP,
>> pvmw->pte is mapped. But for HugeTLB pages, pvmw->pte is not mapped and set
>> to the relevant page table entry. So in page_vma_mapped_walk_done(), we may
>> do pte_unmap() for HugeTLB pte which is not mapped. Fix this by checking
>> pvmw->page against PageHuge before trying to do pte_unmap().
>>
>
> What are the runtime consequences of this? Is there a workload which
> is known to trigger it?
>
Not yet. This should not be backported. My bad. Sorry about it.
> IOW, how do we justify a -stable backport of this fix?
> >>
>> --- a/include/linux/rmap.h
>> +++ b/include/linux/rmap.h
>> @@ -213,7 +213,8 @@ struct page_vma_mapped_walk {
>>
>> static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
>> {
>> - if (pvmw->pte)
>> + /* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
>> + if (pvmw->pte && !PageHuge(pvmw->page))
>> pte_unmap(pvmw->pte);
>> if (pvmw->ptl)
>> spin_unlock(pvmw->ptl);
>> --
>> 2.19.1
> .
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-01-28 1:56 UTC | newest]
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2021-01-27 9:33 [PATCH] mm/rmap: Fix potential pte_unmap on an not mapped pte Miaohe Lin
2021-01-28 0:09 ` Andrew Morton
2021-01-28 1:54 ` Miaohe Lin
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