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base/memory, hotplug: fix a kernel oops in show_valid_zones()

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Reading a sysfs "memoryN/valid_zones" file leads to the following oops
when the first page of a range is not backed by struct page.
show_valid_zones() assumes that 'start_pfn' is always valid for
page_zone().

 BUG: unable to handle kernel paging request at ffffea017a000000
 IP: show_valid_zones+0x6f/0x160

This issue may happen on x86-64 systems with 64GiB or more memory since
their memory block size is bumped up to 2GiB.  [1] An example of such
systems is desribed below.  0x3240000000 is only aligned by 1GiB and
this memory block starts from 0x3200000000, which is not backed by
struct page.

 BIOS-e820: [mem 0x0000003240000000-0x000000603fffffff] usable

Since test_pages_in_a_zone() already checks holes, fix this issue by
extending this function to return 'valid_start' and 'valid_end' for a
given range.  show_valid_zones() then proceeds with the valid range.

[1] 'Commit bdee237c03 ("x86: mm: Use 2GB memory block size on
    large-memory x86-64 systems")'

Link: http://lkml.kernel.org/r/20170127222149.30893-3-toshi.kani@hpe.com
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Zhang Zhen <zhenzhang.zhang@huawei.com>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: <stable@vger.kernel.org>	[4.4+]

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Toshi Kani 2017-02-03 13:13:23 -08:00 • committed by Linus Torvalds
parent deb88a2a19
commit a96dfddbcc
3 changed files with 23 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

12
drivers/base/memory.c
View file

@ -389,33 +389,33 @@ static ssize_t show_valid_zones(struct device *dev,
{
struct memory_block *mem = to_memory_block(dev);
unsigned long start_pfn, end_pfn;
unsigned long valid_start, valid_end, valid_pages;
unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
struct page *first_page;
struct zone *zone;
int zone_shift = 0;
start_pfn = section_nr_to_pfn(mem->start_section_nr);
end_pfn = start_pfn + nr_pages;
first_page = pfn_to_page(start_pfn);
/* The block contains more than one zone can not be offlined. */
if (!test_pages_in_a_zone(start_pfn, end_pfn))
if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end))
return sprintf(buf, "none\n");
zone = page_zone(first_page);
zone = page_zone(pfn_to_page(valid_start));
valid_pages = valid_end - valid_start;
/* MMOP_ONLINE_KEEP */
sprintf(buf, "%s", zone->name);
/* MMOP_ONLINE_KERNEL */
zone_can_shift(start_pfn, nr_pages, ZONE_NORMAL, &zone_shift);
zone_can_shift(valid_start, valid_pages, ZONE_NORMAL, &zone_shift);
if (zone_shift) {
strcat(buf, " ");
strcat(buf, (zone + zone_shift)->name);
}
/* MMOP_ONLINE_MOVABLE */
zone_can_shift(start_pfn, nr_pages, ZONE_MOVABLE, &zone_shift);
zone_can_shift(valid_start, valid_pages, ZONE_MOVABLE, &zone_shift);
if (zone_shift) {
strcat(buf, " ");
strcat(buf, (zone + zone_shift)->name);