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SubjectRe: [PATCH] mm/vmalloc: move 'area->pages' after if statement
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On 8/30/19 10:50 PM, Andrew Morton wrote:
> On Fri, 30 Aug 2019 12:57:16 +0900 Austin Kim <austindh.kim@gmail.com> 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 <vbabka@suse.cz>

> --- 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;
> _
>
>

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