Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-13 Thread Toshiaki Makita
On 2018/04/12 17:03, Dmitry Vyukov wrote:
> On Thu, Apr 12, 2018 at 10:01 AM, syzbot
>  wrote:
>> Hello,
>>
>> syzbot hit the following crash on https://github.com/google/kmsan.git/master
>> commit
>> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +)
>> kmsan: temporarily disable visitAsmInstruction() to help syzbot
>> syzbot dashboard link:
>> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>> Raw console output:
>> https://syzkaller.appspot.com/x/log.txt?id=535651643762
>> Kernel config:
>> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
>> compiler: clang version 7.0.0 (trunk 329391)
> 
> +Toshiaki as this seems to be related to the recent vlan tagging changes.

seems not...
"Uninit was stored to memory at:" shows uninitialized memory was stored
before where I modified the code (skb_reorder_vlan_header).

I'm not sure what this uninit memory means.
To me it looks like the memory is initialized by user provided data.

(iov in packet sock -> skb->data -> skb->protocol)

The reproducer provides 4 bytes after ethernet header, so it should be
sufficient for a vlan tag. This will set skb->len to 4 and fill the
4-byte contents in packet_snd(). skb_vlan_untag() is reading the user
provided 4-byte skb->data. It is ensured that skb_vlan_untag() does not
read beyond skb->len since it calls pskb_may_pull(). At this point I am
failing to find what I am missing.

> This also seems to be related to
> https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ
> 
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
>> 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: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
>> [inline]
>> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
>> [inline]
>> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
>> net/core/dev.c:4545
>> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
>> 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+0x185/0x1d0 lib/dump_stack.c:53
>>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>  __read_once_size include/linux/compiler.h:197 [inline]
>>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>>  __netif_receive_skb net/core/dev.c:4627 [inline]
>>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>>  napi_poll net/core/dev.c:5705 [inline]
>>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>>  
>>  do_softirq kernel/softirq.c:329 [inline]
>>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>  sock_sendmsg net/socket.c:640 [inline]
>>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>>  vfs_writev fs/read_write.c:977 [inline]
>>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>> RIP: 0033:0x455259
>> RSP: 002b:7fb53ede8c68 EFLAGS: 0246 ORIG_RAX: 0014
>> RAX: ffda RBX: 7fb53ede96d4 RCX: 00455259
>> RDX: 0001 RSI: 200010c0 RDI: 0013
>> RBP: 0072bea0 R08:  R09: 
>> R10:  R11: 0246 R12: 
>> R13: 06cd R14: 006fd3d8 R15: 
>>
>> Uninit was stored to memory at:
>>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>>  kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
>>  kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
>>  __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
>>  skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
>>  __netif_receive_skb_core+0x70a/0x4a80 

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-13 Thread Toshiaki Makita
On 2018/04/12 17:03, Dmitry Vyukov wrote:
> On Thu, Apr 12, 2018 at 10:01 AM, syzbot
>  wrote:
>> Hello,
>>
>> syzbot hit the following crash on https://github.com/google/kmsan.git/master
>> commit
>> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +)
>> kmsan: temporarily disable visitAsmInstruction() to help syzbot
>> syzbot dashboard link:
>> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>> Raw console output:
>> https://syzkaller.appspot.com/x/log.txt?id=535651643762
>> Kernel config:
>> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
>> compiler: clang version 7.0.0 (trunk 329391)
> 
> +Toshiaki as this seems to be related to the recent vlan tagging changes.

seems not...
"Uninit was stored to memory at:" shows uninitialized memory was stored
before where I modified the code (skb_reorder_vlan_header).

I'm not sure what this uninit memory means.
To me it looks like the memory is initialized by user provided data.

(iov in packet sock -> skb->data -> skb->protocol)

The reproducer provides 4 bytes after ethernet header, so it should be
sufficient for a vlan tag. This will set skb->len to 4 and fill the
4-byte contents in packet_snd(). skb_vlan_untag() is reading the user
provided 4-byte skb->data. It is ensured that skb_vlan_untag() does not
read beyond skb->len since it calls pskb_may_pull(). At this point I am
failing to find what I am missing.

> This also seems to be related to
> https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ
> 
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
>> 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: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
>> [inline]
>> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
>> [inline]
>> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
>> net/core/dev.c:4545
>> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
>> 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+0x185/0x1d0 lib/dump_stack.c:53
>>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>  __read_once_size include/linux/compiler.h:197 [inline]
>>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>>  __netif_receive_skb net/core/dev.c:4627 [inline]
>>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>>  napi_poll net/core/dev.c:5705 [inline]
>>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>>  
>>  do_softirq kernel/softirq.c:329 [inline]
>>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>  sock_sendmsg net/socket.c:640 [inline]
>>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>>  vfs_writev fs/read_write.c:977 [inline]
>>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>> RIP: 0033:0x455259
>> RSP: 002b:7fb53ede8c68 EFLAGS: 0246 ORIG_RAX: 0014
>> RAX: ffda RBX: 7fb53ede96d4 RCX: 00455259
>> RDX: 0001 RSI: 200010c0 RDI: 0013
>> RBP: 0072bea0 R08:  R09: 
>> R10:  R11: 0246 R12: 
>> R13: 06cd R14: 006fd3d8 R15: 
>>
>> Uninit was stored to memory at:
>>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>>  kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
>>  kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
>>  __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
>>  skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
>>  __netif_receive_skb_core+0x70a/0x4a80 net/core/dev.c:4460
>>  __netif_receive_skb net/core/dev.c:4627 

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-13 Thread Dmitry Vyukov
On Fri, Apr 13, 2018 at 10:20 AM, Toshiaki Makita
 wrote:
> On 2018/04/12 17:03, Dmitry Vyukov wrote:
>> On Thu, Apr 12, 2018 at 10:01 AM, syzbot
>>  wrote:
>>> Hello,
>>>
>>> syzbot hit the following crash on https://github.com/google/kmsan.git/master
>>> commit
>>> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +)
>>> kmsan: temporarily disable visitAsmInstruction() to help syzbot
>>> syzbot dashboard link:
>>> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>>>
>>> Unfortunately, I don't have any reproducer for this crash yet.
>>> Raw console output:
>>> https://syzkaller.appspot.com/x/log.txt?id=535651643762
>>> Kernel config:
>>> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
>>> compiler: clang version 7.0.0 (trunk 329391)
>>
>> +Toshiaki as this seems to be related to the recent vlan tagging changes.
>
> seems not...
> "Uninit was stored to memory at:" shows uninitialized memory was stored
> before where I modified the code (skb_reorder_vlan_header).
>
> I'm not sure what this uninit memory means.
> To me it looks like the memory is initialized by user provided data.
>
> (iov in packet sock -> skb->data -> skb->protocol)
>
> The reproducer provides 4 bytes after ethernet header, so it should be
> sufficient for a vlan tag. This will set skb->len to 4 and fill the
> 4-byte contents in packet_snd(). skb_vlan_untag() is reading the user
> provided 4-byte skb->data. It is ensured that skb_vlan_untag() does not
> read beyond skb->len since it calls pskb_may_pull(). At this point I am
> failing to find what I am missing.

Eric,

You mentioned something about assumption that the
__vlan_insert_inner_tag() helper would only be called from
__netif_receive_skb_core(). Can you elaborate?



>> This also seems to be related to
>> https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ
>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
>>> 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: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
>>> [inline]
>>> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
>>> [inline]
>>> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
>>> net/core/dev.c:4545
>>> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
>>> 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+0x185/0x1d0 lib/dump_stack.c:53
>>>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>>>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>>  __read_once_size include/linux/compiler.h:197 [inline]
>>>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>>>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>>>  __netif_receive_skb net/core/dev.c:4627 [inline]
>>>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>>>  napi_poll net/core/dev.c:5705 [inline]
>>>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>>>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>>>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>>>  
>>>  do_softirq kernel/softirq.c:329 [inline]
>>>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>>>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>>>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>>>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>>>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>>  sock_sendmsg net/socket.c:640 [inline]
>>>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>>>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>>>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>>>  vfs_writev fs/read_write.c:977 [inline]
>>>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>>>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>>>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>>>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>>>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>>> RIP: 0033:0x455259
>>> RSP: 002b:7fb53ede8c68 EFLAGS: 0246 ORIG_RAX: 0014
>>> RAX: ffda RBX: 7fb53ede96d4 RCX: 00455259
>>> RDX: 0001 RSI: 200010c0 RDI: 0013
>>> RBP: 0072bea0 R08:  R09: 
>>> R10:  R11: 0246 R12: 
>>> R13: 06cd R14: 006fd3d8 R15: 
>>>
>>> Uninit was stored 

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-13 Thread Dmitry Vyukov
On Fri, Apr 13, 2018 at 10:20 AM, Toshiaki Makita
 wrote:
> On 2018/04/12 17:03, Dmitry Vyukov wrote:
>> On Thu, Apr 12, 2018 at 10:01 AM, syzbot
>>  wrote:
>>> Hello,
>>>
>>> syzbot hit the following crash on https://github.com/google/kmsan.git/master
>>> commit
>>> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +)
>>> kmsan: temporarily disable visitAsmInstruction() to help syzbot
>>> syzbot dashboard link:
>>> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>>>
>>> Unfortunately, I don't have any reproducer for this crash yet.
>>> Raw console output:
>>> https://syzkaller.appspot.com/x/log.txt?id=535651643762
>>> Kernel config:
>>> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
>>> compiler: clang version 7.0.0 (trunk 329391)
>>
>> +Toshiaki as this seems to be related to the recent vlan tagging changes.
>
> seems not...
> "Uninit was stored to memory at:" shows uninitialized memory was stored
> before where I modified the code (skb_reorder_vlan_header).
>
> I'm not sure what this uninit memory means.
> To me it looks like the memory is initialized by user provided data.
>
> (iov in packet sock -> skb->data -> skb->protocol)
>
> The reproducer provides 4 bytes after ethernet header, so it should be
> sufficient for a vlan tag. This will set skb->len to 4 and fill the
> 4-byte contents in packet_snd(). skb_vlan_untag() is reading the user
> provided 4-byte skb->data. It is ensured that skb_vlan_untag() does not
> read beyond skb->len since it calls pskb_may_pull(). At this point I am
> failing to find what I am missing.

Eric,

You mentioned something about assumption that the
__vlan_insert_inner_tag() helper would only be called from
__netif_receive_skb_core(). Can you elaborate?



>> This also seems to be related to
>> https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ
>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
>>> 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: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
>>> [inline]
>>> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
>>> [inline]
>>> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
>>> net/core/dev.c:4545
>>> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
>>> 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+0x185/0x1d0 lib/dump_stack.c:53
>>>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>>>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>>  __read_once_size include/linux/compiler.h:197 [inline]
>>>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>>>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>>>  __netif_receive_skb net/core/dev.c:4627 [inline]
>>>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>>>  napi_poll net/core/dev.c:5705 [inline]
>>>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>>>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>>>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>>>  
>>>  do_softirq kernel/softirq.c:329 [inline]
>>>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>>>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>>>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>>>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>>>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>>  sock_sendmsg net/socket.c:640 [inline]
>>>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>>>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>>>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>>>  vfs_writev fs/read_write.c:977 [inline]
>>>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>>>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>>>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>>>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>>>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>>> RIP: 0033:0x455259
>>> RSP: 002b:7fb53ede8c68 EFLAGS: 0246 ORIG_RAX: 0014
>>> RAX: ffda RBX: 7fb53ede96d4 RCX: 00455259
>>> RDX: 0001 RSI: 200010c0 RDI: 0013
>>> RBP: 0072bea0 R08:  R09: 
>>> R10:  R11: 0246 R12: 
>>> R13: 06cd R14: 006fd3d8 R15: 
>>>
>>> Uninit was stored to memory at:
>>>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>>>  

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-12 Thread syzbot
syzbot has found reproducer for the following crash on  
https://github.com/google/kmsan.git/master commit

35ff515e4bda2646f6c881d33951c306ea9c282a (Tue Apr 10 08:59:43 2018 +)
Merge pull request #11 from parkerduckworth/readme
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa


So far this crash happened 3 times on  
https://github.com/google/kmsan.git/master.

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=455991623680
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=4590273065648128
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=4631921027973120
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=6627248707860932248

compiler: clang version 7.0.0 (trunk 329391)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed.

==
BUG: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197  
[inline]
BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908  
[inline]
BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80  
net/core/dev.c:4545

CPU: 0 PID: 3514 Comm: syzkaller031167 Not tainted 4.16.0+ #83
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+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
 __read_once_size include/linux/compiler.h:197 [inline]
 deliver_ptype_list_skb net/core/dev.c:1908 [inline]
 __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
 __netif_receive_skb net/core/dev.c:4627 [inline]
 process_backlog+0x62d/0xe20 net/core/dev.c:5307
 napi_poll net/core/dev.c:5705 [inline]
 net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
 __do_softirq+0x56d/0x93d kernel/softirq.c:285
 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
 
 do_softirq kernel/softirq.c:329 [inline]
 __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
 local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
 rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
 __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
 packet_snd net/packet/af_packet.c:2944 [inline]
 packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg net/socket.c:640 [inline]
 sock_write_iter+0x3b9/0x470 net/socket.c:909
 do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
 do_iter_write+0x30d/0xd40 fs/read_write.c:932
 vfs_writev fs/read_write.c:977 [inline]
 do_writev+0x3c9/0x830 fs/read_write.c:1012
 SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
 SyS_writev+0x56/0x80 fs/read_write.c:1082
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43ffb9
RSP: 002b:7ffd42187708 EFLAGS: 0217 ORIG_RAX: 0014
RAX: ffda RBX: 004002c8 RCX: 0043ffb9
RDX: 0001 RSI: 200010c0 RDI: 0003
RBP: 006ca018 R08: 004002c8 R09: 004002c8
R10: 004002c8 R11: 0217 R12: 004018e0
R13: 00401970 R14:  R15: 

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
 skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
 __netif_receive_skb_core+0x70a/0x4a80 net/core/dev.c:4460
 __netif_receive_skb net/core/dev.c:4627 [inline]
 process_backlog+0x62d/0xe20 net/core/dev.c:5307
 napi_poll net/core/dev.c:5705 [inline]
 net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
 __do_softirq+0x56d/0x93d kernel/softirq.c:285
Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
 kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
 slab_post_alloc_hook mm/slab.h:445 [inline]
 slab_alloc_node mm/slub.c:2737 [inline]
 __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
 __kmalloc_reserve net/core/skbuff.c:138 [inline]
 __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
 alloc_skb include/linux/skbuff.h:984 [inline]
 alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
 sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2085
 packet_alloc_skb net/packet/af_packet.c:2803 [inline]
 packet_snd net/packet/af_packet.c:2894 [inline]
 packet_sendmsg+0x6444/0x8a10 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg net/socket.c:640 [inline]
 sock_write_iter+0x3b9/0x470 

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-12 Thread syzbot
syzbot has found reproducer for the following crash on  
https://github.com/google/kmsan.git/master commit

35ff515e4bda2646f6c881d33951c306ea9c282a (Tue Apr 10 08:59:43 2018 +)
Merge pull request #11 from parkerduckworth/readme
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa


So far this crash happened 3 times on  
https://github.com/google/kmsan.git/master.

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=455991623680
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=4590273065648128
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=4631921027973120
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=6627248707860932248

compiler: clang version 7.0.0 (trunk 329391)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed.

==
BUG: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197  
[inline]
BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908  
[inline]
BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80  
net/core/dev.c:4545

CPU: 0 PID: 3514 Comm: syzkaller031167 Not tainted 4.16.0+ #83
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+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
 __read_once_size include/linux/compiler.h:197 [inline]
 deliver_ptype_list_skb net/core/dev.c:1908 [inline]
 __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
 __netif_receive_skb net/core/dev.c:4627 [inline]
 process_backlog+0x62d/0xe20 net/core/dev.c:5307
 napi_poll net/core/dev.c:5705 [inline]
 net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
 __do_softirq+0x56d/0x93d kernel/softirq.c:285
 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
 
 do_softirq kernel/softirq.c:329 [inline]
 __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
 local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
 rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
 __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
 packet_snd net/packet/af_packet.c:2944 [inline]
 packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg net/socket.c:640 [inline]
 sock_write_iter+0x3b9/0x470 net/socket.c:909
 do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
 do_iter_write+0x30d/0xd40 fs/read_write.c:932
 vfs_writev fs/read_write.c:977 [inline]
 do_writev+0x3c9/0x830 fs/read_write.c:1012
 SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
 SyS_writev+0x56/0x80 fs/read_write.c:1082
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x43ffb9
RSP: 002b:7ffd42187708 EFLAGS: 0217 ORIG_RAX: 0014
RAX: ffda RBX: 004002c8 RCX: 0043ffb9
RDX: 0001 RSI: 200010c0 RDI: 0003
RBP: 006ca018 R08: 004002c8 R09: 004002c8
R10: 004002c8 R11: 0217 R12: 004018e0
R13: 00401970 R14:  R15: 

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
 skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
 __netif_receive_skb_core+0x70a/0x4a80 net/core/dev.c:4460
 __netif_receive_skb net/core/dev.c:4627 [inline]
 process_backlog+0x62d/0xe20 net/core/dev.c:5307
 napi_poll net/core/dev.c:5705 [inline]
 net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
 __do_softirq+0x56d/0x93d kernel/softirq.c:285
Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
 kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
 slab_post_alloc_hook mm/slab.h:445 [inline]
 slab_alloc_node mm/slub.c:2737 [inline]
 __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
 __kmalloc_reserve net/core/skbuff.c:138 [inline]
 __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
 alloc_skb include/linux/skbuff.h:984 [inline]
 alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
 sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2085
 packet_alloc_skb net/packet/af_packet.c:2803 [inline]
 packet_snd net/packet/af_packet.c:2894 [inline]
 packet_sendmsg+0x6444/0x8a10 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg net/socket.c:640 [inline]
 sock_write_iter+0x3b9/0x470 

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-12 Thread Dmitry Vyukov
On Thu, Apr 12, 2018 at 10:01 AM, syzbot
 wrote:
> Hello,
>
> syzbot hit the following crash on https://github.com/google/kmsan.git/master
> commit
> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +)
> kmsan: temporarily disable visitAsmInstruction() to help syzbot
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=535651643762
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
> compiler: clang version 7.0.0 (trunk 329391)

+Toshiaki as this seems to be related to the recent vlan tagging changes.
This also seems to be related to
https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
> 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: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
> [inline]
> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
> [inline]
> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
> net/core/dev.c:4545
> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
> 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+0x185/0x1d0 lib/dump_stack.c:53
>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>  __read_once_size include/linux/compiler.h:197 [inline]
>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>  __netif_receive_skb net/core/dev.c:4627 [inline]
>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>  napi_poll net/core/dev.c:5705 [inline]
>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>  
>  do_softirq kernel/softirq.c:329 [inline]
>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>  packet_snd net/packet/af_packet.c:2944 [inline]
>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>  sock_sendmsg_nosec net/socket.c:630 [inline]
>  sock_sendmsg net/socket.c:640 [inline]
>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>  vfs_writev fs/read_write.c:977 [inline]
>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> RIP: 0033:0x455259
> RSP: 002b:7fb53ede8c68 EFLAGS: 0246 ORIG_RAX: 0014
> RAX: ffda RBX: 7fb53ede96d4 RCX: 00455259
> RDX: 0001 RSI: 200010c0 RDI: 0013
> RBP: 0072bea0 R08:  R09: 
> R10:  R11: 0246 R12: 
> R13: 06cd R14: 006fd3d8 R15: 
>
> Uninit was stored to memory at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>  kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
>  kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
>  __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
>  skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
>  __netif_receive_skb_core+0x70a/0x4a80 net/core/dev.c:4460
>  __netif_receive_skb net/core/dev.c:4627 [inline]
>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>  napi_poll net/core/dev.c:5705 [inline]
>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
> Uninit was created at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
>  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
>  kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
>  slab_post_alloc_hook mm/slab.h:445 [inline]
>  slab_alloc_node mm/slub.c:2737 [inline]
>  __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
>  __kmalloc_reserve net/core/skbuff.c:138 [inline]
>  __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
>  alloc_skb include/linux/skbuff.h:984 [inline]
>  alloc_skb_with_frags+0x1d4/0xb20 

Re: KMSAN: uninit-value in __netif_receive_skb_core

2018-04-12 Thread Dmitry Vyukov
On Thu, Apr 12, 2018 at 10:01 AM, syzbot
 wrote:
> Hello,
>
> syzbot hit the following crash on https://github.com/google/kmsan.git/master
> commit
> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +)
> kmsan: temporarily disable visitAsmInstruction() to help syzbot
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=535651643762
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
> compiler: clang version 7.0.0 (trunk 329391)

+Toshiaki as this seems to be related to the recent vlan tagging changes.
This also seems to be related to
https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b202b720866414295...@syzkaller.appspotmail.com
> 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: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
> [inline]
> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
> [inline]
> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
> net/core/dev.c:4545
> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
> 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+0x185/0x1d0 lib/dump_stack.c:53
>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>  __read_once_size include/linux/compiler.h:197 [inline]
>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>  __netif_receive_skb net/core/dev.c:4627 [inline]
>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>  napi_poll net/core/dev.c:5705 [inline]
>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>  
>  do_softirq kernel/softirq.c:329 [inline]
>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>  packet_snd net/packet/af_packet.c:2944 [inline]
>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>  sock_sendmsg_nosec net/socket.c:630 [inline]
>  sock_sendmsg net/socket.c:640 [inline]
>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>  vfs_writev fs/read_write.c:977 [inline]
>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> RIP: 0033:0x455259
> RSP: 002b:7fb53ede8c68 EFLAGS: 0246 ORIG_RAX: 0014
> RAX: ffda RBX: 7fb53ede96d4 RCX: 00455259
> RDX: 0001 RSI: 200010c0 RDI: 0013
> RBP: 0072bea0 R08:  R09: 
> R10:  R11: 0246 R12: 
> R13: 06cd R14: 006fd3d8 R15: 
>
> Uninit was stored to memory at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>  kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
>  kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
>  __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
>  skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
>  __netif_receive_skb_core+0x70a/0x4a80 net/core/dev.c:4460
>  __netif_receive_skb net/core/dev.c:4627 [inline]
>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>  napi_poll net/core/dev.c:5705 [inline]
>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
> Uninit was created at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
>  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
>  kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
>  slab_post_alloc_hook mm/slab.h:445 [inline]
>  slab_alloc_node mm/slub.c:2737 [inline]
>  __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
>  __kmalloc_reserve net/core/skbuff.c:138 [inline]
>  __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
>  alloc_skb include/linux/skbuff.h:984 [inline]
>  alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
>