2019-05-13 03:05:10

by Weikang shi

Subject: [PATCH] mm: Change count_mm_mlocked_page_nr return type

From: swkhack <[email protected]>

In 64-bit machine,the value of "vma->vm_end - vma->vm_start"
maybe negative in 32bit int and the "count >> PAGE_SHIFT"'s result
will be wrong.So change the local variable and return
value to unsigned long will fix the problem.

Signed-off-by: swkhack <[email protected]>
---
mm/mlock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index 080f3b364..d614163f5 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -636,11 +636,11 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
* is also counted.
* Return value: previously mlocked page counts
*/
-static int count_mm_mlocked_page_nr(struct mm_struct *mm,
+static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
unsigned long start, size_t len)
{
struct vm_area_struct *vma;
- int count = 0;
+ unsigned long count = 0;

if (mm == NULL)
mm = current->mm;
--
2.17.1

2019-05-13 09:20:17

by Michal Hocko

Subject: Re: [PATCH] mm: Change count_mm_mlocked_page_nr return type

On Mon 13-05-19 10:37:01, Weikang shi wrote:
> From: swkhack <[email protected]>
>
> In 64-bit machine,the value of "vma->vm_end - vma->vm_start"
> maybe negative in 32bit int and the "count >> PAGE_SHIFT"'s result
> will be wrong.So change the local variable and return
> value to unsigned long will fix the problem.
>
> Signed-off-by: swkhack <[email protected]>

Fixes: 0cf2f6f6dc60 ("mm: mlock: check against vma for actual mlock() size")

Acked-by: Michal Hocko <[email protected]>

Most users probably never noticed because large mlocked areas are not
allowed by default. So I am not really sure this is worth backporting to
stable trees.

> ---
> mm/mlock.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 080f3b364..d614163f5 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -636,11 +636,11 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
> * is also counted.
> * Return value: previously mlocked page counts
> */
> -static int count_mm_mlocked_page_nr(struct mm_struct *mm,
> +static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
> unsigned long start, size_t len)
> {
> struct vm_area_struct *vma;
> - int count = 0;
> + unsigned long count = 0;
>
> if (mm == NULL)
> mm = current->mm;
> --
> 2.17.1

--
Michal Hocko
SUSE Labs