* [PATCH v2] thp: use is_zero_pfn only after pte_present check
@ 2015-10-13 2:38 Minchan Kim
2015-10-13 5:41 ` Greg Kroah-Hartman
2015-10-13 7:28 ` Vlastimil Babka
0 siblings, 2 replies; 5+ messages in thread
From: Minchan Kim @ 2015-10-13 2:38 UTC (permalink / raw)
To: Andrew Morton
Cc: Kirill A. Shutemov, Mel Gorman, Vlastimil Babka,
Andrea Arcangeli, Hugh Dickins, Rik van Riel, linux-kernel,
linux-mm, Greg Kroah-Hartman, Minchan Kim, stable,
Kirill A. Shutemov
Use is_zero_pfn on pteval only after pte_present check on pteval
(It might be better idea to introduce is_zero_pte where checks
pte_present first). Otherwise, it could work with swap or
migration entry and if pte_pfn's result is equal to zero_pfn
by chance, we lose user's data in __collapse_huge_page_copy.
So if you're luck, the application is segfaulted and finally you
could see below message when the application is exit.
BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3
Cc: <stable@vger.kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
Hello Greg,
This patch should go to -stable but when you will apply it
after merging of linus tree, it will be surely conflicted due
to userfaultfd part.
I want to know how to handle it.
Thanks.
mm/huge_memory.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4b06b8db9df2..bbac913f96bc 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2206,7 +2206,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
- if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
+ if (pte_none(pteval) || (pte_present(pteval) &&
+ is_zero_pfn(pte_pfn(pteval)))) {
if (!userfaultfd_armed(vma) &&
++none_or_zero <= khugepaged_max_ptes_none)
continue;
--
1.9.1
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] thp: use is_zero_pfn only after pte_present check
2015-10-13 2:38 [PATCH v2] thp: use is_zero_pfn only after pte_present check Minchan Kim
@ 2015-10-13 5:41 ` Greg Kroah-Hartman
2015-10-13 6:26 ` Minchan Kim
2015-10-13 7:28 ` Vlastimil Babka
1 sibling, 1 reply; 5+ messages in thread
From: Greg Kroah-Hartman @ 2015-10-13 5:41 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, Kirill A. Shutemov, Mel Gorman, Vlastimil Babka,
Andrea Arcangeli, Hugh Dickins, Rik van Riel, linux-kernel,
linux-mm, stable, Kirill A. Shutemov
On Tue, Oct 13, 2015 at 11:38:38AM +0900, Minchan Kim wrote:
> Use is_zero_pfn on pteval only after pte_present check on pteval
> (It might be better idea to introduce is_zero_pte where checks
> pte_present first). Otherwise, it could work with swap or
> migration entry and if pte_pfn's result is equal to zero_pfn
> by chance, we lose user's data in __collapse_huge_page_copy.
> So if you're luck, the application is segfaulted and finally you
> could see below message when the application is exit.
>
> BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3
>
> Cc: <stable@vger.kernel.org>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> Hello Greg,
>
> This patch should go to -stable but when you will apply it
> after merging of linus tree, it will be surely conflicted due
> to userfaultfd part.
>
> I want to know how to handle it.
You will get an automated email saying it didn't apply and then you
provide a backported version. Or you send a properly backported version
to stable@vger.kernel.org before then, with the git commit id of the
patch in Linus's tree.
thanks,
greg k-h
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] thp: use is_zero_pfn only after pte_present check
2015-10-13 5:41 ` Greg Kroah-Hartman
@ 2015-10-13 6:26 ` Minchan Kim
0 siblings, 0 replies; 5+ messages in thread
From: Minchan Kim @ 2015-10-13 6:26 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Andrew Morton, Kirill A. Shutemov, Mel Gorman, Vlastimil Babka,
Andrea Arcangeli, Hugh Dickins, Rik van Riel, linux-kernel,
linux-mm, stable, Kirill A. Shutemov
On Mon, Oct 12, 2015 at 10:41:24PM -0700, Greg Kroah-Hartman wrote:
> On Tue, Oct 13, 2015 at 11:38:38AM +0900, Minchan Kim wrote:
> > Use is_zero_pfn on pteval only after pte_present check on pteval
> > (It might be better idea to introduce is_zero_pte where checks
> > pte_present first). Otherwise, it could work with swap or
> > migration entry and if pte_pfn's result is equal to zero_pfn
> > by chance, we lose user's data in __collapse_huge_page_copy.
> > So if you're luck, the application is segfaulted and finally you
> > could see below message when the application is exit.
> >
> > BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3
> >
> > Cc: <stable@vger.kernel.org>
> > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > ---
> > Hello Greg,
> >
> > This patch should go to -stable but when you will apply it
> > after merging of linus tree, it will be surely conflicted due
> > to userfaultfd part.
> >
> > I want to know how to handle it.
>
> You will get an automated email saying it didn't apply and then you
> provide a backported version. Or you send a properly backported version
> to stable@vger.kernel.org before then, with the git commit id of the
> patch in Linus's tree.
Okay, I will send a right version when I received automatd email.
Thanks.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] thp: use is_zero_pfn only after pte_present check
2015-10-13 2:38 [PATCH v2] thp: use is_zero_pfn only after pte_present check Minchan Kim
2015-10-13 5:41 ` Greg Kroah-Hartman
@ 2015-10-13 7:28 ` Vlastimil Babka
2015-10-13 9:10 ` Minchan Kim
1 sibling, 1 reply; 5+ messages in thread
From: Vlastimil Babka @ 2015-10-13 7:28 UTC (permalink / raw)
To: Minchan Kim, Andrew Morton
Cc: Kirill A. Shutemov, Mel Gorman, Andrea Arcangeli, Hugh Dickins,
Rik van Riel, linux-kernel, linux-mm, Greg Kroah-Hartman, stable,
Kirill A. Shutemov
On 10/13/2015 04:38 AM, Minchan Kim wrote:
> Use is_zero_pfn on pteval only after pte_present check on pteval
> (It might be better idea to introduce is_zero_pte where checks
> pte_present first). Otherwise, it could work with swap or
> migration entry and if pte_pfn's result is equal to zero_pfn
> by chance, we lose user's data in __collapse_huge_page_copy.
> So if you're luck, the application is segfaulted and finally you
> could see below message when the application is exit.
>
> BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3
>
> Cc: <stable@vger.kernel.org>
More specific:
Cc: <stable@vger.kernel.org> # 4.1+
Fixes: ca0984caa823 ("mm: incorporate zero pages into transparent huge
pages")
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> Hello Greg,
>
> This patch should go to -stable but when you will apply it
> after merging of linus tree, it will be surely conflicted due
> to userfaultfd part.
>
> I want to know how to handle it.
>
> Thanks.
>
> mm/huge_memory.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4b06b8db9df2..bbac913f96bc 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2206,7 +2206,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
> _pte++, address += PAGE_SIZE) {
> pte_t pteval = *_pte;
> - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> + if (pte_none(pteval) || (pte_present(pteval) &&
> + is_zero_pfn(pte_pfn(pteval)))) {
> if (!userfaultfd_armed(vma) &&
> ++none_or_zero <= khugepaged_max_ptes_none)
> continue;
>
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] thp: use is_zero_pfn only after pte_present check
2015-10-13 7:28 ` Vlastimil Babka
@ 2015-10-13 9:10 ` Minchan Kim
0 siblings, 0 replies; 5+ messages in thread
From: Minchan Kim @ 2015-10-13 9:10 UTC (permalink / raw)
To: Vlastimil Babka
Cc: Andrew Morton, Kirill A. Shutemov, Mel Gorman, Andrea Arcangeli,
Hugh Dickins, Rik van Riel, linux-kernel, linux-mm,
Greg Kroah-Hartman, stable, Kirill A. Shutemov
On Tue, Oct 13, 2015 at 09:28:23AM +0200, Vlastimil Babka wrote:
> On 10/13/2015 04:38 AM, Minchan Kim wrote:
> >Use is_zero_pfn on pteval only after pte_present check on pteval
> >(It might be better idea to introduce is_zero_pte where checks
> >pte_present first). Otherwise, it could work with swap or
> >migration entry and if pte_pfn's result is equal to zero_pfn
> >by chance, we lose user's data in __collapse_huge_page_copy.
> >So if you're luck, the application is segfaulted and finally you
> >could see below message when the application is exit.
> >
> >BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3
> >
> >Cc: <stable@vger.kernel.org>
>
> More specific:
> Cc: <stable@vger.kernel.org> # 4.1+
> Fixes: ca0984caa823 ("mm: incorporate zero pages into transparent
> huge pages")
>
> >Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
Thanks for the detail and review, Vlastimil.
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2015-10-13 2:38 [PATCH v2] thp: use is_zero_pfn only after pte_present check Minchan Kim
2015-10-13 5:41 ` Greg Kroah-Hartman
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2015-10-13 7:28 ` Vlastimil Babka
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