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

[Cong Wang]

On Mon, Jan 8, 2018 at 6:58 AM, syzbot
<syzbot+aae58876fb5a1fad0a4b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzkaller hit the following crash on
> b2cd1df66037e7c4697c7e40496bf7e4a5e16a2d
> 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.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
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> Reported-by: syzbot+aae58876fb5a1fad0a4b@xxxxxxxxxxxxxxxxxxxxxxxxx
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> ==================================================================
> BUG: KASAN: use-after-free in tipc_group_size+0x40/0x50 net/tipc/group.c:158
> Read of size 2 at addr ffff8801c08ba280 by task syzkaller447710/3513
>
> CPU: 0 PID: 3513 Comm: syzkaller447710 Not tainted 4.15.0-rc7+ #252
> 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_load2_noabort+0x14/0x20 mm/kasan/report.c:428
>  tipc_group_size+0x40/0x50 net/tipc/group.c:158
>  tipc_poll+0x374/0x4f0 net/tipc/socket.c:739

Seems we have to lock the sock for tipc_group_size() in
tipc_poll().


>  sock_poll+0x141/0x320 net/socket.c:1117
>  do_pollfd fs/select.c:822 [inline]
>  do_poll fs/select.c:872 [inline]
>  do_sys_poll+0x715/0x10b0 fs/select.c:966
>  SYSC_poll fs/select.c:1024 [inline]
>  SyS_poll+0x10d/0x450 fs/select.c:1012
>  entry_SYSCALL_64_fastpath+0x23/0x9a
> RIP: 0033:0x445cb9
> RSP: 002b:00007f04886b1ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000007
> RAX: ffffffffffffffda RBX: 00000000006dac3c RCX: 0000000000445cb9
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000020fa2ff8
> RBP: 00000000006dac38 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffc84d56d7f R14: 00007f04886b29c0 R15: 0000000000000005
>
> Allocated by task 3510:
>  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:3610
>  kmalloc include/linux/slab.h:499 [inline]
>  kzalloc include/linux/slab.h:688 [inline]
>  tipc_group_create+0x116/0x9c0 net/tipc/group.c:167
>  tipc_sk_join net/tipc/socket.c:2747 [inline]
>  tipc_setsockopt+0x249/0xc10 net/tipc/socket.c:2861
>  SYSC_setsockopt net/socket.c:1829 [inline]
>  SyS_setsockopt+0x189/0x360 net/socket.c:1808
>  entry_SYSCALL_64_fastpath+0x23/0x9a
>
> Freed by task 3510:
>  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:3488 [inline]
>  kfree+0xd6/0x260 mm/slab.c:3803
>  tipc_group_delete+0x2c8/0x3d0 net/tipc/group.c:206
>  tipc_sk_join net/tipc/socket.c:2760 [inline]
>  tipc_setsockopt+0xb0d/0xc10 net/tipc/socket.c:2861
>  SYSC_setsockopt net/socket.c:1829 [inline]
>  SyS_setsockopt+0x189/0x360 net/socket.c:1808
>  entry_SYSCALL_64_fastpath+0x23/0x9a
>
> The buggy address belongs to the object at ffff8801c08ba200
>  which belongs to the cache kmalloc-192 of size 192
> The buggy address is located 128 bytes inside of
>  192-byte region [ffff8801c08ba200, ffff8801c08ba2c0)
> The buggy address belongs to the page:
> page:ffffea0007022e80 count:1 mapcount:0 mapping:ffff8801c08ba000 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801c08ba000 0000000000000000 0000000100000010
> raw: ffffea00071338a0 ffffea0006fe2360 ffff8801dac00040 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801c08ba180: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff8801c08ba200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801c08ba280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>
>                    ^
>  ffff8801c08ba300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801c08ba380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
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