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SubjectRe: [PATCH] mm: Fix NULL ptr dereference in __count_immobile_pages
On Tue, 10 Jan 2012 17:30:22 +0100
Michal Hocko <mhocko@suse.cz> wrote:

> This patch fixes the following NULL ptr dereference caused by
> cat /sys/devices/system/memory/memory0/removable:

Which is world-readable, I assume?

> ...
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5608,6 +5608,17 @@ __count_immobile_pages(struct zone *zone, struct page *page, int count)
> bool is_pageblock_removable_nolock(struct page *page)
> {
> struct zone *zone = page_zone(page);
> + unsigned long pfn = page_to_pfn(page);
> +
> + /*
> + * We have to be careful here because we are iterating over memory
> + * sections which are not zone aware so we might end up outside of
> + * the zone but still within the section.
> + */
> + if (!zone || zone->zone_start_pfn > pfn ||
> + zone->zone_start_pfn + zone->spanned_pages <= pfn)
> + return false;
> +
> return __count_immobile_pages(zone, page, 0);
> }

So I propose that we backport it into -stable?


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