Re: KASAN: use-after-free Read in __do_page_fault

[Dmitry Vyukov]

On Mon, Oct 30, 2017 at 10:12 PM, syzbot
<bot+6a5269ce759a7bb12754ed9622076dc93f65a1f6@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> 887c8ba753fbe809ba93fa3cfd0cc46db18d37d4
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
>
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> BUG: KASAN: use-after-free in arch_local_irq_enable
> arch/x86/include/asm/paravirt.h:787 [inline]
> BUG: KASAN: use-after-free in __do_page_fault+0xc03/0xd60
> arch/x86/mm/fault.c:1357
> Read of size 8 at addr ffff8801cbfd3090 by task syz-executor7/3660
>
> CPU: 1 PID: 3660 Comm: syz-executor7 Not tainted 4.14.0-rc3+ #23
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:16 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:52
>  print_address_description+0x73/0x250 mm/kasan/report.c:252
>  kasan_report_error mm/kasan/report.c:351 [inline]
>  kasan_report+0x25b/0x340 mm/kasan/report.c:409
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
>  arch_local_irq_enable arch/x86/include/asm/paravirt.h:787 [inline]
>  __do_page_fault+0xc03/0xd60 arch/x86/mm/fault.c:1357
>  do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1520
>  page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1066
> RIP: 0023:0x8073f4f
> RSP: 002b:00000000f7f89bd0 EFLAGS: 00010202
> RAX: 00000000f7f89c8c RBX: 0000000000000400 RCX: 000000000000000e
> RDX: 00000000f7f8aa88 RSI: 0000000020012fe0 RDI: 00000000f7f89c8c
> RBP: 0000000008128000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 3660:
>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
>  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
>  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3561
>  kmem_cache_zalloc include/linux/slab.h:656 [inline]
>  mmap_region+0x7ee/0x15a0 mm/mmap.c:1658
>  do_mmap+0x6a1/0xd50 mm/mmap.c:1468
>  do_mmap_pgoff include/linux/mm.h:2150 [inline]
>  vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
>  SYSC_mmap_pgoff mm/mmap.c:1518 [inline]
>  SyS_mmap_pgoff+0x23b/0x5f0 mm/mmap.c:1476
>  do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
>  do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
>  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124
>
> Freed by task 3667:
>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
>  __cache_free mm/slab.c:3503 [inline]
>  kmem_cache_free+0x77/0x280 mm/slab.c:3763
>  remove_vma+0x162/0x1b0 mm/mmap.c:176
>  remove_vma_list mm/mmap.c:2475 [inline]
>  do_munmap+0x82a/0xdf0 mm/mmap.c:2714
>  mmap_region+0x59e/0x15a0 mm/mmap.c:1631
>  do_mmap+0x6a1/0xd50 mm/mmap.c:1468
>  do_mmap_pgoff include/linux/mm.h:2150 [inline]
>  vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
>  SYSC_mmap_pgoff mm/mmap.c:1518 [inline]
>  SyS_mmap_pgoff+0x23b/0x5f0 mm/mmap.c:1476
>  do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
>  do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
>  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124
>
> The buggy address belongs to the object at ffff8801cbfd3040
>  which belongs to the cache vm_area_struct of size 200
> The buggy address is located 80 bytes inside of
>  200-byte region [ffff8801cbfd3040, ffff8801cbfd3108)
> The buggy address belongs to the page:
> page:ffffea00072ff4c0 count:1 mapcount:0 mapping:ffff8801cbfd3040 index:0x0
> flags: 0x200000000000100(slab)
> raw: 0200000000000100 ffff8801cbfd3040 0000000000000000 000000010000000f
> raw: ffffea000730c7a0 ffffea00072ff7a0 ffff8801dae069c0 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801cbfd2f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801cbfd3000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>>
>> ffff8801cbfd3080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>                          ^
>  ffff8801cbfd3100: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb
>  ffff8801cbfd3180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================


I guess this is more related to mm rather than x86, so +mm maintainers.
This continues to happen, in particular on upstream
781402340475144bb360e32bb7437fa4b84cadc3 (Oct 28).


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