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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

20
mm/memory_hotplug.c
View file

@ -1484,10 +1484,13 @@ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
/*
* Confirm all pages in a range [start, end) belong to the same zone.
* When true, return its valid [start, end).
*/
int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
unsigned long *valid_start, unsigned long *valid_end)
{
unsigned long pfn, sec_end_pfn;
unsigned long start, end;
struct zone *zone = NULL;
struct page *page;
int i;
@ -1509,14 +1512,20 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
page = pfn_to_page(pfn + i);
if (zone && page_zone(page) != zone)
return 0;
if (!zone)
start = pfn + i;
zone = page_zone(page);
end = pfn + MAX_ORDER_NR_PAGES;
}
}
if (zone)
if (zone) {
*valid_start = start;
*valid_end = end;
return 1;
else
} else {
return 0;
}
}
/*
@ -1843,6 +1852,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
long offlined_pages;
int ret, drain, retry_max, node;
unsigned long flags;
unsigned long valid_start, valid_end;
struct zone *zone;
struct memory_notify arg;
@ -1853,10 +1863,10 @@ static int __ref __offline_pages(unsigned long start_pfn,
return -EINVAL;
/* This makes hotplug much easier...and readable.
we assume this for now. .*/
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 -EINVAL;
zone = page_zone(pfn_to_page(start_pfn));
zone = page_zone(pfn_to_page(valid_start));
node = zone_to_nid(zone);
nr_pages = end_pfn - start_pfn;