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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>
This commit is contained in:
Andrew Banman 2015-12-29 14:54:25 -08:00 committed by Linus Torvalds
parent b5a8bc338e
commit 5f0f2887f4
1 changed files with 19 additions and 12 deletions
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31
mm/memory_hotplug.c
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@ -1375,23 +1375,30 @@ 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 += 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))
i++;
if (i == MAX_ORDER_NR_PAGES)
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;
page = pfn_to_page(pfn + i);
if (zone && page_zone(page) != zone)
return 0;
zone = page_zone(page);
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))
i++;
if (i == MAX_ORDER_NR_PAGES)
continue;
page = pfn_to_page(pfn + i);
if (zone && page_zone(page) != zone)
return 0;
zone = page_zone(page);
}
}
return 1;
}