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SubjectRe: [PATCH v4] mm/page_owner: clamp read count to PAGE_SIZE
On Fri, 2 Nov 2018 01:00:07 +0800 <miles.chen@mediatek.com> wrote:

> From: Miles Chen <miles.chen@mediatek.com>
>
> The page owner read might allocate a large size of memory with
> a large read count. Allocation fails can easily occur when doing
> high order allocations.
>
> Clamp buffer size to PAGE_SIZE to avoid arbitrary size allocation
> and avoid allocation fails due to high order allocation.
>
> ...
>
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -351,6 +351,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
> .skip = 0
> };
>
> + count = count > PAGE_SIZE ? PAGE_SIZE : count;
> kbuf = kmalloc(count, GFP_KERNEL);
> if (!kbuf)
> return -ENOMEM;

A bit tidier:

--- a/mm/page_owner.c~mm-page_owner-clamp-read-count-to-page_size-fix
+++ a/mm/page_owner.c
@@ -351,7 +351,7 @@ print_page_owner(char __user *buf, size_
.skip = 0
};

- count = count > PAGE_SIZE ? PAGE_SIZE : count;
+ count = min_t(size_t, count, PAGE_SIZE);
kbuf = kmalloc(count, GFP_KERNEL);
if (!kbuf)
return -ENOMEM;
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