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Commit a96dfddb authored by Toshi Kani's avatar Toshi Kani Committed by Linus Torvalds
Browse files

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

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 bdee237c ("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: default avatarToshi 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent deb88a2a

drivers/base/memory.c

+6 −6
Original line number Diff line number Diff line
@@ -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);

include/linux/memory_hotplug.h

+2 −1
Original line number Diff line number Diff line
@@ -85,7 +85,8 @@ extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages); 
extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);

/* VM interface that may be used by firmware interface */

extern int online_pages(unsigned long, unsigned long, int);

extern int test_pages_in_a_zone(unsigned long, unsigned long);

extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,

	unsigned long *valid_start, unsigned long *valid_end);

extern void __offline_isolated_pages(unsigned long, unsigned long);



typedef void (*online_page_callback_t)(struct page *page);

mm/memory_hotplug.c

+15 −5
Original line number Diff line number Diff line
@@ -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;
@@ -1509,15 +1512,21 @@ 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;

	}

}



/*

 * Scan pfn range [start,end) to find movable/migratable pages (LRU pages
@@ -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;