Commit 5f0f2887 authored Dec 29, 2015 by Andrew Banman Committed by Linus Torvalds Dec 29, 2015

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: Andrew Banman <abanman@sgi.com>
Acked-by: Alex 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus 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;
		}

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