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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 bdee237c0343 ("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+]

Toshi Kani committed 9 years ago

Commit a96dfdd1 parent deb88a23 files · +23 −12Browse files

Unified · Split

3 files
  1. drivers/base/memory.c +6 −6
  2. include/linux/memory_hotplug.h +2 −1
  3. mm/memory_hotplug.c +15 −5
drivers/base/memory.c+6−6
@@ -389,33 +389,33 @@ static ssize_t show_valid_zones(struct device *dev, · 388 unmodified lines
389389 {
390390 struct memory_block *mem = to_memory_block(dev);
391391 unsigned long start_pfn, end_pfn;
392+ unsigned long valid_start, valid_end, valid_pages;
392393 unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
393− struct page *first_page;
394394 struct zone *zone;
395395 int zone_shift = 0;
396396
397397 start_pfn = section_nr_to_pfn(mem->start_section_nr);
398398 end_pfn = start_pfn + nr_pages;
399− first_page = pfn_to_page(start_pfn);
400399
401400 /* The block contains more than one zone can not be offlined. */
402− if (!test_pages_in_a_zone(start_pfn, end_pfn))
401+ if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end))
403402 return sprintf(buf, "none\n");
404403
405− zone = page_zone(first_page);
404+ zone = page_zone(pfn_to_page(valid_start));
405+ valid_pages = valid_end - valid_start;
406406
407407 /* MMOP_ONLINE_KEEP */
408408 sprintf(buf, "%s", zone->name);
409409
410410 /* MMOP_ONLINE_KERNEL */
411− zone_can_shift(start_pfn, nr_pages, ZONE_NORMAL, &zone_shift);
411+ zone_can_shift(valid_start, valid_pages, ZONE_NORMAL, &zone_shift);
412412 if (zone_shift) {
413413 strcat(buf, " ");
414414 strcat(buf, (zone + zone_shift)->name);
415415 }
416416
417417 /* MMOP_ONLINE_MOVABLE */
418− zone_can_shift(start_pfn, nr_pages, ZONE_MOVABLE, &zone_shift);
418+ zone_can_shift(valid_start, valid_pages, ZONE_MOVABLE, &zone_shift);
419419 if (zone_shift) {
420420 strcat(buf, " ");
421421 strcat(buf, (zone + zone_shift)->name);
include/linux/memory_hotplug.h+2−1
@@ -85,7 +85,8 @@ extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages); · 84 unmodified lines
8585 extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
8686 /* VM interface that may be used by firmware interface */
8787 extern int online_pages(unsigned long, unsigned long, int);
88−extern int test_pages_in_a_zone(unsigned long, unsigned long);
88+extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
89+ unsigned long *valid_start, unsigned long *valid_end);
8990 extern void __offline_isolated_pages(unsigned long, unsigned long);
9091
9192 typedef void (*online_page_callback_t)(struct page *page);
mm/memory_hotplug.c+15−5
@@ -1484,10 +1484,13 @@ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) · 1483 unmodified lines
14841484
14851485 /*
14861486 * Confirm all pages in a range [start, end) belong to the same zone.
1487+ * When true, return its valid [start, end).
14871488 */
1488−int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
1489+int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
1490+ unsigned long *valid_start, unsigned long *valid_end)
14891491 {
14901492 unsigned long pfn, sec_end_pfn;
1493+ unsigned long start, end;
14911494 struct zone *zone = NULL;
14921495 struct page *page;
14931496 int i;
@@ -1509,14 +1512,20 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn) · 15 unmodified lines
15091512 page = pfn_to_page(pfn + i);
15101513 if (zone && page_zone(page) != zone)
15111514 return 0;
1515+ if (!zone)
1516+ start = pfn + i;
15121517 zone = page_zone(page);
1518+ end = pfn + MAX_ORDER_NR_PAGES;
15131519 }
15141520 }
15151521
1516− if (zone)
1522+ if (zone) {
1523+ *valid_start = start;
1524+ *valid_end = end;
15171525 return 1;
1518− else
1526+ } else {
15191527 return 0;
1528+ }
15201529 }
15211530
15221531 /*
@@ -1843,6 +1852,7 @@ static int __ref __offline_pages(unsigned long start_pfn, · 320 unmodified lines
18431852 long offlined_pages;
18441853 int ret, drain, retry_max, node;
18451854 unsigned long flags;
1855+ unsigned long valid_start, valid_end;
18461856 struct zone *zone;
18471857 struct memory_notify arg;
18481858
@@ -1853,10 +1863,10 @@ static int __ref __offline_pages(unsigned long start_pfn, · 4 unmodified lines
18531863 return -EINVAL;
18541864 /* This makes hotplug much easier...and readable.
18551865 we assume this for now. .*/
1856− if (!test_pages_in_a_zone(start_pfn, end_pfn))
1866+ if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end))
18571867 return -EINVAL;
18581868
1859− zone = page_zone(pfn_to_page(start_pfn));
1869+ zone = page_zone(pfn_to_page(valid_start));
18601870 node = zone_to_nid(zone);
18611871 nr_pages = end_pfn - start_pfn;
18621872