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[PATCH 4.4 16/29] mm/memory_hotplug.c: check start_pfn in test_pages_in_a_zone()

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Toshi Kani <toshi.kani@hpe.com>

commit deb88a2a19e85842d79ba96b05031739ec327ff4 upstream.

Patch series "fix a kernel oops when reading sysfs valid_zones", v2.

A sysfs memory file is created for each 2GiB memory block on x86-64 when
the system has 64GiB or more memory.  [1] When the start address of a
memory block is not backed by struct page, i.e.  a memory range is not
aligned by 2GiB, reading its 'valid_zones' attribute file leads to a
kernel oops.  This issue was observed on multiple x86-64 systems with
more than 64GiB of memory.  This patch-set fixes this issue.

Patch 1 first fixes an issue in test_pages_in_a_zone(), which does not
test the start section.

Patch 2 then fixes the kernel oops by extending test_pages_in_a_zone()
to return valid [start, end).

Note for stable kernels: The memory block size change was made by commit
bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64
systems"), which was accepted to 3.9.  However, this patch-set depends
on (and fixes) the change to test_pages_in_a_zone() made by commit
5f0f2887f4de ("mm/memory_hotplug.c: check for missing sections in
test_pages_in_a_zone()"), which was accepted to 4.4.

So, I recommend that we backport it up to 4.4.

[1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on
    large-memory x86-64 systems")'

This patch (of 2):

test_pages_in_a_zone() does not check 'start_pfn' when it is aligned by
section since 'sec_end_pfn' is set equal to 'pfn'.  Since this function
is called for testing the range of a sysfs memory file, 'start_pfn' is
always aligned by section.

Fix it by properly setting 'sec_end_pfn' to the next section pfn.

Also make sure that this function returns 1 only when the range belongs
to a zone.

Link: http://lkml.kernel.org/r/20170127222149.30893-2-toshi.kani@hpe.com
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Andrew Banman <abanman@sgi.com>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/memory_hotplug.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1371,7 +1371,7 @@ int is_mem_section_removable(unsigned lo
 }
 
 /*
- * Confirm all pages in a range [start, end) is belongs to the same zone.
+ * Confirm all pages in a range [start, end) belong to the same zone.
  */
 int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
 {
@@ -1379,9 +1379,9 @@ int test_pages_in_a_zone(unsigned long s
 	struct zone *zone = NULL;
 	struct page *page;
 	int i;
-	for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn);
+	for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn + 1);
 	     pfn < end_pfn;
-	     pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) {
+	     pfn = sec_end_pfn, sec_end_pfn += PAGES_PER_SECTION) {
 		/* Make sure the memory section is present first */
 		if (!present_section_nr(pfn_to_section_nr(pfn)))
 			continue;
@@ -1400,7 +1400,11 @@ int test_pages_in_a_zone(unsigned long s
 			zone = page_zone(page);
 		}
 	}
-	return 1;
+
+	if (zone)
+		return 1;
+	else
+		return 0;
 }
 
 /*

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[PATCH 4.4 00/29] 4.4.48-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 23/29] USB: serial: qcserial: add Dell DW5570 QDL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 13/29] svcrpc: fix oops in absence of krb5 module Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 07/29] perf/core: Fix PERF_RECORD_MMAP2 prot/flags for anonymous memory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 29/29] base/memory, hotplug: fix a kernel oops in show_valid_zones() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 20/29] percpu-refcount: fix reference leak during percpu-atomic transition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 18/29] can: bcm: fix hrtimer/tasklet termination in bcm op removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 24/29] USB: serial: pl2303: add ATEN device ID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 08/29] ata: sata_mv:- Handle return value of devm_ioremap. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 11/29] powerpc: Add missing error check to prom_find_boot_cpu() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 21/29] HID: wacom: Fix poor prox handling in wacom_pl_irq Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 03/29] drm/nouveau/disp/gt215: Fix HDA ELD handling (thus, HDMI audio) on gt215 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 28/29] x86/irq: Make irq activate operations symmetric Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 02/29] ext4: validate s_first_meta_bg at mount time Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 15/29] cifs: initialize file_info_lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 26/29] usb: gadget: f_fs: Assorted buffer overflow checks. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 04/29] drm/nouveau/nv1a,nv1f/disp: fix memory clock rate retrieval Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 13:50 +0100
  [PATCH 4.4 01/29] PCI/ASPM: Handle PCI-to-PCIe bridges as roots of PCIe hierarchies Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 14:00 +0100
  [PATCH 4.4 14/29] zswap: disable changing params if init fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 14:00 +0100
  [PATCH 4.4 16/29] mm/memory_hotplug.c: check start_pfn in test_pages_in_a_zone() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 14:00 +0100
  [PATCH 4.4 12/29] NFSD: Fix a null reference case in find_or_create_lock_stateid() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 14:00 +0100
  [PATCH 4.4 19/29] mmc: sdhci: Ignore unexpected CARD_INT interrupts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-07 14:00 +0100
  Re: [PATCH 4.4 00/29] 4.4.48-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-02-07 17:00 +0100
  Re: [PATCH 4.4 00/29] 4.4.48-stable review Guenter Roeck <linux@roeck-us.net> - 2017-02-07 22:50 +0100
  Re: [PATCH 4.4 00/29] 4.4.48-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-08 07:40 +0100
    Re: [PATCH 4.4 00/29] 4.4.48-stable review Kevin Hilman <khilman@baylibre.com> - 2017-02-08 20:50 +0100
      Re: [PATCH 4.4 00/29] 4.4.48-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-08 21:10 +0100

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