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[Kamal Mostafa <kamal@xxxxxxxxxxxxx>]

This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
trusty' to 'verification-done-trusty'.

If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: verification-needed-trusty

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https://bugs.launchpad.net/bugs/1572562

Title:
  KASan: out of bounds access in isolate_migratepages_range

Status in linux package in Ubuntu:
  Confirmed
Status in linux source package in Trusty:
  Fix Committed

Bug description:
  [Impact]
  In the v3.13.0-76 kernel with KASan backported.
  The following error message could be observed during the kernel
  building stress test of the command[1]: "./parallel-73670.sh -r 2 -k 40"
  That means building 40 kernels in the same time with 2 rounds.

  Bad access happens when we read page->mapping->flags, and
  page->mapping is a pointer to anon_vma which is already freed
  in the do_exit path.

  ==================================================================
  BUG: KASan: out of bounds access in isolate_migratepages_range+0x663/0xb30 at addr ffff880279cc76d1
  Read of size 8 by task cc1/27473
  =============================================================================
  BUG anon_vma (Not tainted): kasan: bad access detected
  -----------------------------------------------------------------------------

  Disabling lock debugging due to kernel taint
  INFO: Allocated in anon_vma_prepare+0x189/0x250 age=7323 cpu=16 pid=31029
          __slab_alloc+0x4f8/0x560
          kmem_cache_alloc+0x18b/0x1e0
          anon_vma_prepare+0x189/0x250
          do_wp_page+0x837/0xb10
          handle_mm_fault+0x884/0x1160
          __do_page_fault+0x218/0x750
          do_page_fault+0x1a/0x70
          page_fault+0x28/0x30
  INFO: Freed in __put_anon_vma+0x69/0xe0 age=8588 cpu=4 pid=29418
          __slab_free+0x2ab/0x3f0
          kmem_cache_free+0x1c1/0x200
          __put_anon_vma+0x69/0xe0
          unlink_anon_vmas+0x2a8/0x320
          free_pgtables+0x50/0x1c0
          exit_mmap+0xca/0x1e0
          mmput+0x82/0x1b0
          do_exit+0x391/0x1060
          do_group_exit+0x86/0x130
          SyS_exit_group+0x1d/0x20
          system_call_fastpath+0x1a/0x1f
  INFO: Slab 0xffffea0009e73100 objects=43 used=30 fp=0xffff880279cc67a8 flags=0x2ffff0000004080
  INFO: Object 0xffff880279cc7658 @offset=13912 fp=0xffff880279cc7c38

  Bytes b4 ffff880279cc7648: 10 00 00 00 5b 17 00 00 ef 25 6b 03 01 00 00 00  ....[....%k.....
  Object ffff880279cc7658: 58 76 cc 79 02 88 ff ff 00 00 00 00 00 00 00 00  Xv.y............
  Object ffff880279cc7668: 00 00 00 00 5a 5a 5a 5a 70 76 cc 79 02 88 ff ff  ....ZZZZpv.y....
  Object ffff880279cc7678: 70 76 cc 79 02 88 ff ff 01 00 00 00 03 00 00 00  pv.y............
  Object ffff880279cc7688: 58 76 cc 79 02 88 ff ff b8 2a 20 31 02 88 ff ff  Xv.y.....* 1....
  CPU: 8 PID: 27473 Comm: cc1 Tainted: G    B         3.13.0-76-generic #120hf00073670v20160120b0h5d3e6ab
  Hardware name: Cisco Systems Inc UCSC-C220-M3L/UCSC-C220-M3L, BIOS C220M3.2.0.3.0.080120140402 08/01/2014
   ffffea0009e73100 ffff880736bbf750 ffffffff81a6e195 ffff8804e881b840
   ffff880736bbf780 ffffffff81244c1d ffff8804e881b840 ffffea0009e73100
   ffff880279cc7658 ffffea001aa99c98 ffff880736bbf7a8 ffffffff8124ad66
  Call Trace:
   [<ffffffff81a6e195>] dump_stack+0x45/0x56
   [<ffffffff81244c1d>] print_trailer+0xfd/0x170
   [<ffffffff8124ad66>] object_err+0x36/0x40
   [<ffffffff8124cd29>] kasan_report_error+0x1e9/0x3a0
   [<ffffffff8125d9f8>] ? memcg_check_events+0x28/0x380
   [<ffffffff81221c2d>] ? rmap_walk+0x32d/0x340
   [<ffffffff8124d390>] kasan_report+0x40/0x50
   [<ffffffff81205ee3>] ? isolate_migratepages_range+0x663/0xb30
   [<ffffffff8124c019>] __asan_load8+0x69/0xa0
   [<ffffffff81205ee3>] isolate_migratepages_range+0x663/0xb30
   [<ffffffff811dc5e7>] ? zone_watermark_ok+0x57/0x70
   [<ffffffff812067c6>] compact_zone+0x416/0x700
   [<ffffffff81206b45>] compact_zone_order+0x95/0x100
   [<ffffffff81207002>] try_to_compact_pages+0x102/0x1a0
   [<ffffffff811e21e6>] __alloc_pages_direct_compact+0x96/0x290
   [<ffffffff811e2d5e>] __alloc_pages_nodemask+0x97e/0xc40
   [<ffffffff8123ce24>] alloc_pages_vma+0xb4/0x200
   [<ffffffff812572ca>] do_huge_pmd_anonymous_page+0x13a/0x490
   [<ffffffff8120f072>] ? do_numa_page+0x192/0x200
   [<ffffffff81210c07>] handle_mm_fault+0x267/0x1160
   [<ffffffff81a7d028>] __do_page_fault+0x218/0x750
   [<ffffffff8121aead>] ? do_mmap_pgoff+0x47d/0x500
   [<ffffffff811fd699>] ? vm_mmap_pgoff+0xa9/0xd0
   [<ffffffff81a7d57a>] do_page_fault+0x1a/0x70
   [<ffffffff81a785a8>] page_fault+0x28/0x30
  Memory state around the buggy address:
   ffff880279cc7580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
   ffff880279cc7600: fc fc fc fc fc fc fc fc fc fc fc 00 00 00 00 00
  >ffff880279cc7680: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
                                                   ^
   ffff880279cc7700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
   ffff880279cc7780: fc fc fc fc fc fc fc fc fc fc 00 00 00 00 00 00
  ==================================================================

  gavin@rotom:~/ddebs/ddebs-3.13.0-76.120hf00073670v20160120b0h5d3e6ab$ addr2line 0xffffffff81205ee3 -e usr/lib/debug/boot/vmlinux-3.13.0-76-generic -fi
  constant_test_bit
  /home/gavin/ubuntu-trusty-amd64/arch/x86/include/asm/bitops.h:313
  mapping_balloon
  /home/gavin/ubuntu-trusty-amd64/include/linux/pagemap.h:69
  __is_movable_balloon_page
  /home/gavin/ubuntu-trusty-amd64/include/linux/balloon_compaction.h:131
  balloon_page_movable
  /home/gavin/ubuntu-trusty-amd64/include/linux/balloon_compaction.h:156
  isolate_migratepages_range
  /home/gavin/ubuntu-trusty-amd64/mm/compaction.c:554

  >8------------------8<
  /home/gavin/ubuntu-trusty-amd64/arch/x86/include/asm/bitops.h:313
  310 static __always_inline int constant_test_bit(long nr, const volatile unsigned long *addr)
  311 {
  312         return ((1UL << (nr & (BITS_PER_LONG-1))) &
  313                 (addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
  314 }
  >8------------------8<
  Related upstream mailing list discussion:
  - mm: compaction: buffer overflow in isolate_migratepages_range
    https://lkml.org/lkml/2014/8/9/162
  - [PATCH v3 1/4] mm/balloon_compaction: redesign ballooned pages management
    http://www.spinics.net/lists/linux-mm/msg79249.html

  [Fix]
  - The first patach is the solution commit which moves the PageBalloon
    check to page->_mapcount.
  d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management")
  - The second one is the patch to remove the isolation check when the
    CONFIG_BALLOON_COMPACTION is not defined.
  4d88e6f7d5ff ("mm/balloon_compaction: fix deflation when compaction is disabled")

  [Test Case]
  Running the following command on the Trusty
  kernel(Ubuntu-3.13.0-86.130) with KASan backported. The bug error
  messages cannot be observed in the dmesg.
  "./parallel-73670.sh -r 2 -k 40"
  That means building 40 kernels in the same time with 2 rounds.

  Reference:
  [1]. http://kernel.ubuntu.com/git/gavinguo/stress-test.git/

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