| From 5f0f2887f4de9508dcf438deab28f1de8070c271 Mon Sep 17 00:00:00 2001 |
| From: Andrew Banman <abanman@sgi.com> |
| Date: Tue, 29 Dec 2015 14:54:25 -0800 |
| Subject: mm/memory_hotplug.c: check for missing sections in |
| test_pages_in_a_zone() |
| |
| commit 5f0f2887f4de9508dcf438deab28f1de8070c271 upstream. |
| |
| 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> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Zefan Li <lizefan@huawei.com> |
| --- |
| mm/memory_hotplug.c | 31 +++++++++++++++++++------------ |
| 1 file changed, 19 insertions(+), 12 deletions(-) |
| |
| --- a/mm/memory_hotplug.c |
| +++ b/mm/memory_hotplug.c |
| @@ -716,23 +716,30 @@ int is_mem_section_removable(unsigned lo |
| */ |
| static 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; |
| } |