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[PATCH 3.10 42/54] mm/memory_hotplug.c: check for missing sections in test_pages_in_a_zone()

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

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

From: Andrew Banman <abanman@sgi.com>

commit 5f0f2887f4de9508dcf438deab28f1de8070c271 upstream.

test_pages_in_a_zone() does not account for the possibility of missing
sections in the given pfn range.  pfn_valid_within always returns 1 when
CONFIG_HOLES_IN_ZONE is not set, allowing invalid pfns from missing
sections to pass the test, leading to a kernel oops.

Wrap an additional pfn loop with PAGES_PER_SECTION granularity to check
for missing sections before proceeding into the zone-check code.

This also prevents a crash from offlining memory devices with missing
sections.  Despite this, it may be a good idea to keep the related patch
'[PATCH 3/3] drivers: memory: prohibit offlining of memory blocks with
missing sections' because missing sections in a memory block may lead to
other problems not covered by the scope of this fix.

Signed-off-by: Andrew Banman <abanman@sgi.com>
Acked-by: Alex Thorlton <athorlton@sgi.com>
Cc: Russ Anderson <rja@sgi.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Seth Jennings <sjennings@variantweb.net>
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 |   31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1209,23 +1209,30 @@ int is_mem_section_removable(unsigned lo
  */
 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
 {
-	unsigned long pfn;
+	unsigned long pfn, sec_end_pfn;
 	struct zone *zone = NULL;
 	struct page *page;
 	int i;
-	for (pfn = start_pfn;
+	for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn);
 	     pfn < end_pfn;
-	     pfn += MAX_ORDER_NR_PAGES) {
-		i = 0;
-		/* This is just a CONFIG_HOLES_IN_ZONE check.*/
-		while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
-			i++;
-		if (i == MAX_ORDER_NR_PAGES)
+	     pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) {
+		/* Make sure the memory section is present first */
+		if (!present_section_nr(pfn_to_section_nr(pfn)))
 			continue;
-		page = pfn_to_page(pfn + i);
-		if (zone && page_zone(page) != zone)
-			return 0;
-		zone = page_zone(page);
+		for (; pfn < sec_end_pfn && pfn < end_pfn;
+		     pfn += MAX_ORDER_NR_PAGES) {
+			i = 0;
+			/* This is just a CONFIG_HOLES_IN_ZONE check.*/
+			while ((i < MAX_ORDER_NR_PAGES) &&
+				!pfn_valid_within(pfn + i))
+				i++;
+			if (i == MAX_ORDER_NR_PAGES)
+				continue;
+			page = pfn_to_page(pfn + i);
+			if (zone && page_zone(page) != zone)
+				return 0;
+			zone = page_zone(page);
+		}
 	}
 	return 1;
 }

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[PATCH 3.10 00/54] 3.10.98-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:00 +0100
  [PATCH 3.10 31/54] udf: limit the maximum number of indirect extents in a row Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 32/54] udf: Prevent buffer overrun with multi-byte characters Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 27/54] iio: adis_buffer: Fix out-of-bounds memory access Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 05/54] pty: make sure super_block is still valid in final /dev/tty close Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 19/54] iscsi-target: Fix potential dead-lock during node acl delete Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 04/54] pty: fix possible use after free of tty->driver_data Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 24/54] iio:ad7793: Fix ad7785 product ID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 23/54] scsi: fix soft lockup in scsi_remove_target() on module removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 25/54] iio: lpc32xx_adc: fix warnings caused by enabling unprepared clock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 30/54] nfs: Fix race in __update_open_stateid() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 12/54] tracing: Fix freak link error caused by branch tracer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 26/54] iio:ad5064: Make sure ad5064_i2c_write() returns 0 on success Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:10 +0100
  [PATCH 3.10 53/54] ip6mr: call del_timer_sync() in ip6mr_free_table() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:30 +0100
  [PATCH 3.10 54/54] module: wrapper for symbol name. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:30 +0100
  [PATCH 3.10 36/54] fuse: break infinite loop in fuse_fill_write_pages() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 05:30 +0100
  [PATCH 3.10 41/54] iommu/vt-d: Fix 64-bit accesses to 32-bit DMAR_GSTS_REG Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:00 +0100
  [PATCH 3.10 38/54] Input: elantech - add Fujitsu Lifebook U745 to force crc_enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:10 +0100
  [PATCH 3.10 33/54] udf: Check output buffer length when converting name to CS0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:10 +0100
  [PATCH 3.10 42/54] mm/memory_hotplug.c: check for missing sections in test_pages_in_a_zone() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:10 +0100
  [PATCH 3.10 39/54] Input: elantech - mark protocols v2 and v3 as semi-mt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:10 +0100
  [PATCH 3.10 37/54] mm: soft-offline: check return value in second __get_any_page() call Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:10 +0100
  [PATCH 3.10 17/54] Fix a memory leak in scsi_host_dev_release() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 02/54] wan/x25: Fix use-after-free in x25_asy_open_tty() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 14/54] scsi: restart list search after unlock in scsi_remove_target Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 11/54] tools lib traceevent: Fix output of %llu for 64 bit values read on 32 bit machines Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 01/54] ALSA: seq: Fix double port list deletion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 16/54] iscsi-target: Fix rx_login_comp hang after login failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 18/54] SCSI: Fix NULL pointer dereference in runtime PM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 15/54] scsi_sysfs: Fix queue_ramp_up_period return code Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 13/54] klist: fix starting point removed bug in klist iterators Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 10/54] ptrace: use fsuid, fsgid, effective creds for fs access checks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  [PATCH 3.10 20/54] SCSI: fix crashes in sd and sr runtime PM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-24 06:30 +0100
  Re: [PATCH 3.10 00/54] 3.10.98-stable review Willy Tarreau <w@1wt.eu> - 2016-02-24 17:40 +0100
    Re: [PATCH 3.10 00/54] 3.10.98-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-25 20:10 +0100
  Re: [PATCH 3.10 00/54] 3.10.98-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-02-24 19:30 +0100
  Re: [PATCH 3.10 00/54] 3.10.98-stable review Guenter Roeck <linux@roeck-us.net> - 2016-02-25 06:00 +0100
    Re: [PATCH 3.10 00/54] 3.10.98-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-02-25 17:50 +0100
      Re: [PATCH 3.10 00/54] 3.10.98-stable review Guenter Roeck <linux@roeck-us.net> - 2016-02-25 18:10 +0100

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