2019-08-30 03:58:27

by Austin Kim

Subject: [PATCH] mm/vmalloc: move 'area->pages' after if statement

If !area->pages statement is true where memory allocation fails,
area is freed.

In this case 'area->pages = pages' should not executed.
So move 'area->pages = pages' after if statement.

Signed-off-by: Austin Kim <[email protected]>
---
mm/vmalloc.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b810103..af93ba6 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2416,13 +2416,15 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
} else {
pages = kmalloc_node(array_size, nested_gfp, node);
}
- area->pages = pages;
- if (!area->pages) {
+
+ if (!pages) {
remove_vm_area(area->addr);
kfree(area);
return NULL;
}

+ area->pages = pages;
+
for (i = 0; i < area->nr_pages; i++) {
struct page *page;

--
2.6.2

2019-08-30 05:39:43

by Michal Hocko

Subject: Re: [PATCH] mm/vmalloc: move 'area->pages' after if statement

On Fri 30-08-19 12:57:16, Austin Kim wrote:
> If !area->pages statement is true where memory allocation fails,
> area is freed.
>
> In this case 'area->pages = pages' should not executed.
> So move 'area->pages = pages' after if statement.
>
> Signed-off-by: Austin Kim <[email protected]>

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

Thanks!
> ---
> mm/vmalloc.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index b810103..af93ba6 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2416,13 +2416,15 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> } else {
> pages = kmalloc_node(array_size, nested_gfp, node);
> }
> - area->pages = pages;
> - if (!area->pages) {
> +
> + if (!pages) {
> remove_vm_area(area->addr);
> kfree(area);
> return NULL;
> }
>
> + area->pages = pages;
> +
> for (i = 0; i < area->nr_pages; i++) {
> struct page *page;
>
> --
> 2.6.2
>

--
Michal Hocko
SUSE Labs

2019-08-30 20:51:21

by Andrew Morton

Subject: Re: [PATCH] mm/vmalloc: move 'area->pages' after if statement

On Fri, 30 Aug 2019 12:57:16 +0900 Austin Kim <[email protected]> wrote:

> If !area->pages statement is true where memory allocation fails,
> area is freed.
>
> In this case 'area->pages = pages' should not executed.
> So move 'area->pages = pages' after if statement.
>
> ...
>
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2416,13 +2416,15 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> } else {
> pages = kmalloc_node(array_size, nested_gfp, node);
> }
> - area->pages = pages;
> - if (!area->pages) {
> +
> + if (!pages) {
> remove_vm_area(area->addr);
> kfree(area);
> return NULL;
> }
>
> + area->pages = pages;
> +
> for (i = 0; i < area->nr_pages; i++) {
> struct page *page;
>

Fair enough. But we can/should also do this?

--- a/mm/vmalloc.c~mm-vmalloc-move-area-pages-after-if-statement-fix
+++ a/mm/vmalloc.c
@@ -2409,7 +2409,6 @@ static void *__vmalloc_area_node(struct
nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
array_size = (nr_pages * sizeof(struct page *));

- area->nr_pages = nr_pages;
/* Please note that the recursion is strictly bounded. */
if (array_size > PAGE_SIZE) {
pages = __vmalloc_node(array_size, 1, nested_gfp|highmem_mask,
@@ -2425,6 +2424,7 @@ static void *__vmalloc_area_node(struct
}

area->pages = pages;
+ area->nr_pages = nr_pages;

for (i = 0; i < area->nr_pages; i++) {
struct page *page;
_

2019-09-02 15:30:47

by Vlastimil Babka

Subject: Re: [PATCH] mm/vmalloc: move 'area->pages' after if statement

On 8/30/19 10:50 PM, Andrew Morton wrote:
> On Fri, 30 Aug 2019 12:57:16 +0900 Austin Kim <[email protected]> wrote:
>
>> If !area->pages statement is true where memory allocation fails,
>> area is freed.
>>
>> In this case 'area->pages = pages' should not executed.

That read like a use after free fix and made me wonder about stable,
fixes etc... luckily it's not.

>> So move 'area->pages = pages' after if statement.
>>
>> ...
>>
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -2416,13 +2416,15 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
>> } else {
>> pages = kmalloc_node(array_size, nested_gfp, node);
>> }
>> - area->pages = pages;
>> - if (!area->pages) {
>> +
>> + if (!pages) {
>> remove_vm_area(area->addr);
>> kfree(area);
>> return NULL;
>> }
>>
>> + area->pages = pages;
>> +
>> for (i = 0; i < area->nr_pages; i++) {
>> struct page *page;
>>
>
> Fair enough. But we can/should also do this?

Agreed, same thing.

Acked-by: Vlastimil Babka <[email protected]>

> --- a/mm/vmalloc.c~mm-vmalloc-move-area-pages-after-if-statement-fix
> +++ a/mm/vmalloc.c
> @@ -2409,7 +2409,6 @@ static void *__vmalloc_area_node(struct
> nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
> array_size = (nr_pages * sizeof(struct page *));
>
> - area->nr_pages = nr_pages;
> /* Please note that the recursion is strictly bounded. */
> if (array_size > PAGE_SIZE) {
> pages = __vmalloc_node(array_size, 1, nested_gfp|highmem_mask,
> @@ -2425,6 +2424,7 @@ static void *__vmalloc_area_node(struct
> }
>
> area->pages = pages;
> + area->nr_pages = nr_pages;
>
> for (i = 0; i < area->nr_pages; i++) {
> struct page *page;
> _
>
>

2019-09-02 21:30:29

by Austin Kim

Subject: Re: [PATCH] mm/vmalloc: move 'area->pages' after if statement

2019년 8월 31일 (토) 오전 5:50, Andrew Morton <[email protected]>님이 작성:
>
> On Fri, 30 Aug 2019 12:57:16 +0900 Austin Kim <[email protected]> wrote:
>
> > If !area->pages statement is true where memory allocation fails,
> > area is freed.
> >
> > In this case 'area->pages = pages' should not executed.
> > So move 'area->pages = pages' after if statement.
> >
> > ...
> >
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2416,13 +2416,15 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> > } else {
> > pages = kmalloc_node(array_size, nested_gfp, node);
> > }
> > - area->pages = pages;
> > - if (!area->pages) {
> > +
> > + if (!pages) {
> > remove_vm_area(area->addr);
> > kfree(area);
> > return NULL;
> > }
> >
> > + area->pages = pages;
> > +
> > for (i = 0; i < area->nr_pages; i++) {
> > struct page *page;
> >
>
> Fair enough. But we can/should also do this?

I agreed since it is the same treatment.
Thanks for feedback.

>
> --- a/mm/vmalloc.c~mm-vmalloc-move-area-pages-after-if-statement-fix
> +++ a/mm/vmalloc.c
> @@ -2409,7 +2409,6 @@ static void *__vmalloc_area_node(struct
> nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
> array_size = (nr_pages * sizeof(struct page *));
>
> - area->nr_pages = nr_pages;
> /* Please note that the recursion is strictly bounded. */
> if (array_size > PAGE_SIZE) {
> pages = __vmalloc_node(array_size, 1, nested_gfp|highmem_mask,
> @@ -2425,6 +2424,7 @@ static void *__vmalloc_area_node(struct
> }
>
> area->pages = pages;
> + area->nr_pages = nr_pages;
>
> for (i = 0; i < area->nr_pages; i++) {
> struct page *page;
> _
>