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Commit 5f0f2887 authored by Andrew Banman's avatar Andrew Banman Committed by Linus Torvalds
Browse files

mm/memory_hotplug.c: check for missing sections in test_pages_in_a_zone() 



test_pages_in_a_zone() does not account for the possibility of missing
sections in the given pfn range.  pfn_valid_within always returns 1 when
CONFIG_HOLES_IN_ZONE is not set, allowing invalid pfns from missing
sections to pass the test, leading to a kernel oops.

Wrap an additional pfn loop with PAGES_PER_SECTION granularity to check
for missing sections before proceeding into the zone-check code.

This also prevents a crash from offlining memory devices with missing
sections.  Despite this, it may be a good idea to keep the related patch
'[PATCH 3/3] drivers: memory: prohibit offlining of memory blocks with
missing sections' because missing sections in a memory block may lead to
other problems not covered by the scope of this fix.

Signed-off-by: default avatarAndrew Banman <abanman@sgi.com>
Acked-by: default avatarAlex Thorlton <athorlton@sgi.com>
Cc: Russ Anderson <rja@sgi.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b5a8bc33

mm/memory_hotplug.c

+19 −12
Original line number Diff line number Diff line
@@ -1375,16 +1375,22 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) 
 */

int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)

{

	unsigned long pfn;

	unsigned long pfn, sec_end_pfn;

	struct zone *zone = NULL;

	struct page *page;

	int i;

	for (pfn = start_pfn;

	for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn);

	     pfn < end_pfn;

	     pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) {

		/* Make sure the memory section is present first */

		if (!present_section_nr(pfn_to_section_nr(pfn)))

			continue;

		for (; pfn < sec_end_pfn && pfn < end_pfn;

		     pfn += MAX_ORDER_NR_PAGES) {

			i = 0;

			/* This is just a CONFIG_HOLES_IN_ZONE check.*/

		while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))

			while ((i < MAX_ORDER_NR_PAGES) &&

				!pfn_valid_within(pfn + i))

				i++;

			if (i == MAX_ORDER_NR_PAGES)

				continue;
@@ -1393,6 +1399,7 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) 
				return 0;

			zone = page_zone(page);

		}

	}

	return 1;

}