lkml.org 
[lkml]   [2018]   [Nov]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] mm/page_owner: clamp read count to PAGE_SIZE
On Fri 02-11-18 01:00:07, 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.

It is good to mention that interface is root only so the harm due to
unbounded allocation request is somehow reduced.

I believe we want to use seq_file infrastructure in the long term
solution.

> Change since v3:
> - remove the change in kvmalloc
> - keep kmalloc in page_owner.c
>
> Change since v2:
> - improve kvmalloc, allow sub page allocations fallback to
> vmalloc when CONFIG_HIGHMEM=y
>
> Change since v1:
> - use kvmalloc()
> - clamp buffer size to PAGE_SIZE
>
> Signed-off-by: Miles Chen <miles.chen@mediatek.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Michal Hocko <mhocko@kernel.org>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> mm/page_owner.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 87bc0dfdb52b..b83f295e4eca 100644
> --- 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;
> --
> 2.18.0
>

--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2018-11-01 18:10    [W:1.627 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site