Re: KASAN: slab-out-of-bounds Read in erspan_xmit

[William Tu]

On Mon, Jan 22, 2018 at 2:45 PM, David Ahern <dsahern@xxxxxxxxx> wrote:
> [ cc William Tu ]
>
> On 1/22/18 12:58 PM, syzbot wrote:
>> Hello,
>>
>> syzbot hit the following crash on net-next commit
>> 9d6474e458b13a94a0d5b141f2b8f38adf1991ae (Mon Jan 22 02:55:38 2018 +0000)
>> tun: add missing rcu annotation
>>
>> So far this crash happened 5 times on net-next.
>> C reproducer is attached.
>> syzkaller reproducer is attached.
>> Raw console output is attached.
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached.
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+9723f2d288e49b492cf0@xxxxxxxxxxxxxxxxxxxxxxxxx
>> It will help syzbot understand when the bug is fixed. See footer for
>> details.
>> If you forward the report, please keep this part and the footer.
>>
>> ==================================================================
>> BUG: KASAN: slab-out-of-bounds in erspan_xmit+0x22d4/0x2430
>> net/ipv4/ip_gre.c:735
>> Read of size 2 at addr ffff8801c50bb08b by task syzkaller525754/3647
>>
>> CPU: 0 PID: 3647 Comm: syzkaller525754 Not tainted 4.15.0-rc8+ #203
>> 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_load_n_noabort+0xf/0x20 mm/kasan/report.c:440
>>  erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
>>  __netdev_start_xmit include/linux/netdevice.h:4053 [inline]
>>  netdev_start_xmit include/linux/netdevice.h:4062 [inline]
>>  packet_direct_xmit+0x3ad/0x790 net/packet/af_packet.c:267
>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>  packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2969
>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>  sock_sendmsg+0xca/0x110 net/socket.c:640
>>  SYSC_sendto+0x361/0x5c0 net/socket.c:1721
>>  SyS_sendto+0x40/0x50 net/socket.c:1689
>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>> RIP: 0033:0x445649
>> RSP: 002b:00007ffe82dde5b8 EFLAGS: 00000217 ORIG_RAX: 000000000000002c
>> RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000445649
>> RDX: 0000000000000000 RSI: 0000000020003fd9 RDI: 0000000000000004
>> RBP: 00000000004a78c5 R08: 0000000020008000 R09: 000000000000001c
>> R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000402720
>> R13: 00000000004027b0 R14: 0000000000000000 R15: 0000000000000000
>>
>> Allocated by task 3221:
>>  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:3544
>>  getname_flags+0xcb/0x580 fs/namei.c:138
>>  getname+0x19/0x20 fs/namei.c:209
>>  do_sys_open+0x2e7/0x6d0 fs/open.c:1053
>>  SYSC_open fs/open.c:1077 [inline]
>>  SyS_open+0x2d/0x40 fs/open.c:1072
>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>>
>> Freed by task 3221:
>>  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]
>>  kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
>>  putname+0xee/0x130 fs/namei.c:258
>>  do_sys_open+0x31b/0x6d0 fs/open.c:1068
>>  SYSC_open fs/open.c:1077 [inline]
>>  SyS_open+0x2d/0x40 fs/open.c:1072
>>  entry_SYSCALL_64_fastpath+0x29/0xa0
>>
>> The buggy address belongs to the object at ffff8801c50ba000
>>  which belongs to the cache names_cache of size 4096
>> The buggy address is located 139 bytes to the right of
>>  4096-byte region [ffff8801c50ba000, ffff8801c50bb000)
>> The buggy address belongs to the page:
>> page:ffffea0007142e80 count:1 mapcount:0 mapping:ffff8801c50ba000
>> index:0x0 compound_mapcount: 0
>> flags: 0x2fffc0000008100(slab|head)
>> raw: 02fffc0000008100 ffff8801c50ba000 0000000000000000 0000000100000001
>> raw: ffffea0007145320 ffffea00071433a0 ffff8801dae2c600 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>>  ffff8801c50baf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>  ffff8801c50bb000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ffff8801c50bb080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>                       ^
>>  ffff8801c50bb100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>  ffff8801c50bb180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ==================================================================
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
>> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
>>
>> syzbot will keep track of this bug report.
>> If you forgot to add the Reported-by tag, once the fix for this bug is
>> merged
>> into any tree, please reply to this email with:
>> #syz fix: exact-commit-title
>> If you want to test a patch for this bug, please reply with:
>> #syz test: git://repo/address.git branch
>> and provide the patch inline or as an attachment.
>> To mark this as a duplicate of another syzbot report, please reply with:
>> #syz dup: exact-subject-of-another-report
>> If it's a one-off invalid bug report, please reply with:
>> #syz invalid
>> Note: if the crash happens again, it will cause creation of a new bug
>> report.
>> Note: all commands must start from beginning of the line in the email body.
>

Thanks. I'm working on it.