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* Re: [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset
       [not found] <533efd68.435fe00a.6936.ffffa5e7SMTPIN_ADDED_BROKEN@mx.google.com>
@ 2014-04-04 22:03   ` Andrew Morton
  0 siblings, 0 replies; 4+ messages in thread
From: Andrew Morton @ 2014-04-04 22:03 UTC (permalink / raw)
  To: Naoya Horiguchi
  Cc: linux-kernel, mgorman, andi, sasha.levin, kirill.shutemov,
	aneesh.kumar, linux-mm

On Fri, 04 Apr 2014 14:43:33 -0400 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:

> huge_pte_offset() could return NULL, so we need NULL check to avoid
> potential NULL pointer dereferences.
> 
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2662,7 +2662,8 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
>  				BUG_ON(huge_pte_none(pte));
>  				spin_lock(ptl);
>  				ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> -				if (likely(pte_same(huge_ptep_get(ptep), pte)))
> +				if (likely(ptep &&
> +					   pte_same(huge_ptep_get(ptep), pte)))
>  					goto retry_avoidcopy;
>  				/*
>  				 * race occurs while re-acquiring page table
> @@ -2706,7 +2707,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
>  	 */
>  	spin_lock(ptl);
>  	ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> -	if (likely(pte_same(huge_ptep_get(ptep), pte))) {
> +	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
>  		ClearPagePrivate(new_page);
>  
>  		/* Break COW */

Has anyone been hitting oopses here or was this from code inspection?

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset
@ 2014-04-04 22:03   ` Andrew Morton
  0 siblings, 0 replies; 4+ messages in thread
From: Andrew Morton @ 2014-04-04 22:03 UTC (permalink / raw)
  To: Naoya Horiguchi
  Cc: linux-kernel, mgorman, andi, sasha.levin, kirill.shutemov,
	aneesh.kumar, linux-mm

On Fri, 04 Apr 2014 14:43:33 -0400 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:

> huge_pte_offset() could return NULL, so we need NULL check to avoid
> potential NULL pointer dereferences.
> 
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2662,7 +2662,8 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
>  				BUG_ON(huge_pte_none(pte));
>  				spin_lock(ptl);
>  				ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> -				if (likely(pte_same(huge_ptep_get(ptep), pte)))
> +				if (likely(ptep &&
> +					   pte_same(huge_ptep_get(ptep), pte)))
>  					goto retry_avoidcopy;
>  				/*
>  				 * race occurs while re-acquiring page table
> @@ -2706,7 +2707,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
>  	 */
>  	spin_lock(ptl);
>  	ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> -	if (likely(pte_same(huge_ptep_get(ptep), pte))) {
> +	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
>  		ClearPagePrivate(new_page);
>  
>  		/* Break COW */

Has anyone been hitting oopses here or was this from code inspection?

--
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^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset
  2014-04-04 22:03   ` Andrew Morton
  (?)
@ 2014-04-05  0:04   ` Naoya Horiguchi
  -1 siblings, 0 replies; 4+ messages in thread
From: Naoya Horiguchi @ 2014-04-05  0:04 UTC (permalink / raw)
  To: akpm
  Cc: linux-kernel, mgorman, andi, sasha.levin, kirill.shutemov,
	aneesh.kumar, linux-mm

On Fri, Apr 04, 2014 at 03:03:45PM -0700, Andrew Morton wrote:
> On Fri, 04 Apr 2014 14:43:33 -0400 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:
> 
> > huge_pte_offset() could return NULL, so we need NULL check to avoid
> > potential NULL pointer dereferences.
> > 
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -2662,7 +2662,8 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> >  				BUG_ON(huge_pte_none(pte));
> >  				spin_lock(ptl);
> >  				ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> > -				if (likely(pte_same(huge_ptep_get(ptep), pte)))
> > +				if (likely(ptep &&
> > +					   pte_same(huge_ptep_get(ptep), pte)))
> >  					goto retry_avoidcopy;
> >  				/*
> >  				 * race occurs while re-acquiring page table
> > @@ -2706,7 +2707,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> >  	 */
> >  	spin_lock(ptl);
> >  	ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> > -	if (likely(pte_same(huge_ptep_get(ptep), pte))) {
> > +	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
> >  		ClearPagePrivate(new_page);
> >  
> >  		/* Break COW */
> 
> Has anyone been hitting oopses here or was this from code inspection?

It's from code inspection. This is why I didn't CCed stable.

Naoya

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^ permalink raw reply	[flat|nested] 4+ messages in thread
* [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset
@ 2014-04-04 18:43 Naoya Horiguchi
  0 siblings, 0 replies; 4+ messages in thread
From: Naoya Horiguchi @ 2014-04-04 18:43 UTC (permalink / raw)
  To: linux-kernel
  Cc: akpm, mgorman, andi, sasha.levin, kirill.shutemov, aneesh.kumar,
	linux-mm

huge_pte_offset() could return NULL, so we need NULL check to avoid
potential NULL pointer dereferences.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
 mm/hugetlb.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7222247a590b..b8f2bde6ca53 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2662,7 +2662,8 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 				BUG_ON(huge_pte_none(pte));
 				spin_lock(ptl);
 				ptep = huge_pte_offset(mm, address & huge_page_mask(h));
-				if (likely(pte_same(huge_ptep_get(ptep), pte)))
+				if (likely(ptep &&
+					   pte_same(huge_ptep_get(ptep), pte)))
 					goto retry_avoidcopy;
 				/*
 				 * race occurs while re-acquiring page table
@@ -2706,7 +2707,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 	 */
 	spin_lock(ptl);
 	ptep = huge_pte_offset(mm, address & huge_page_mask(h));
-	if (likely(pte_same(huge_ptep_get(ptep), pte))) {
+	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
 		ClearPagePrivate(new_page);
 
 		/* Break COW */
-- 
1.9.0

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^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-04-05  0:04 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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     [not found] <533efd68.435fe00a.6936.ffffa5e7SMTPIN_ADDED_BROKEN@mx.google.com>
2014-04-04 22:03 ` [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset Andrew Morton
2014-04-04 22:03   ` Andrew Morton
2014-04-05  0:04   ` Naoya Horiguchi
2014-04-04 18:43 Naoya Horiguchi

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