Re: KASAN: use-after-free Write in irq_bypass_register_consumer

[Tianyu Lan]

I reproduced the issue. Will have a look.

-- 
Best regards
Tianyu Lan

2017-12-15 18:14 GMT+08:00 syzbot
<bot+7ad82526b98c64c90062275162dacfa48c20dbd3@xxxxxxxxxxxxxxxxxxxxxxxxx>:
> syzkaller has found reproducer for the following crash on
> 82bcf1def3b5f1251177ad47c44f7e17af039b4b
> git://git.cmpxchg.org/linux-mmots.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> ==================================================================
> BUG: KASAN: use-after-free in __list_add include/linux/list.h:64 [inline]
> BUG: KASAN: use-after-free in list_add include/linux/list.h:79 [inline]
> BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4b4/0x500
> virt/lib/irqbypass.c:217
> Write of size 8 at addr ffff8801cdf51180 by task syzkaller436086/15031
>
> CPU: 1 PID: 15031 Comm: syzkaller436086 Not tainted 4.15.0-rc2-mm1+ #39
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  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_store8_noabort+0x17/0x20 mm/kasan/report.c:435
>  __list_add include/linux/list.h:64 [inline]
>  list_add include/linux/list.h:79 [inline]
>  irq_bypass_register_consumer+0x4b4/0x500 virt/lib/irqbypass.c:217
>  kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
>  kvm_irqfd+0x137f/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
>  kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2992
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>  SYSC_ioctl fs/ioctl.c:701 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>  entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x44d379
> RSP: 002b:00007fc5ff9a9d08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fc5ff9aa700 RCX: 000000000044d379
> RDX: 0000000020080fe0 RSI: 000000004020ae76 RDI: 0000000000000005
> RBP: 00000000007ff900 R08: 00007fc5ff9aa700 R09: 00007fc5ff9aa700
> R10: 00007fc5ff9aa700 R11: 0000000000000246 R12: 0000000000000000
> R13: 00000000007ff8ff R14: 00007fc5ff9aa9c0 R15: 0000000000000000
>
> Allocated by task 15031:
>  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
>  kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3614
>  kmalloc include/linux/slab.h:516 [inline]
>  kzalloc include/linux/slab.h:705 [inline]
>  kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
>  kvm_irqfd+0x16c/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
>  kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2992
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>  SYSC_ioctl fs/ioctl.c:701 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>  entry_SYSCALL_64_fastpath+0x1f/0x96
>
> Freed by task 1402:
>  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:3492 [inline]
>  kfree+0xca/0x250 mm/slab.c:3807
>  irqfd_shutdown+0x13c/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
>  process_one_work+0xbfd/0x1bc0 kernel/workqueue.c:2113
>  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
>  kthread+0x37a/0x440 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
>
> The buggy address belongs to the object at ffff8801cdf51000
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 384 bytes inside of
>  512-byte region [ffff8801cdf51000, ffff8801cdf51200)
> The buggy address belongs to the page:
> page:00000000d08a0d63 count:1 mapcount:0 mapping:00000000d54c7be6 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801cdf51000 0000000000000000 0000000100000006
> raw: ffffea00073a7660 ffffea000737f3a0 ffff8801dac00940 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801cdf51080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801cdf51100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801cdf51180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>                    ^
>  ffff8801cdf51200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801cdf51280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>