[PATCH net 0/2] net: af_packet: be careful when expanding mac header size

[PATCH net 0/2] net: af_packet: be careful when expanding mac header size

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

A recent regression in af_packet needed a preliminary debug patch,
which will presumably be useful for next bugs hunting.

The af_packet fix is to make sure MAC headers are contained in
skb linear part, as GSO stack requests.

Eric Dumazet (2):
  net: add debug info to __skb_pull()
  net/af_packet: make sure to pull mac header

 include/linux/skbuff.h | 9 ++++++++-
 net/packet/af_packet.c | 6 ++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

-- 
2.36.1.255.ge46751e96f-goog

[PATCH net 1/2] net: add debug info to __skb_pull()

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

While analyzing yet another syzbot report, I found the following
patch very useful. It allows to better understand what went wrong.

This debug info is only enabled if CONFIG_DEBUG_NET=y,
which is the case for syzbot builds.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/skbuff.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index da96f0d3e753fb7996631bc9350c0c8e0ec5966e..d3d10556f0faea8c8c1deed5715716d4916011d1 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2696,7 +2696,14 @@ void *skb_pull(struct sk_buff *skb, unsigned int len);
 static inline void *__skb_pull(struct sk_buff *skb, unsigned int len)
 {
 	skb->len -= len;
-	BUG_ON(skb->len < skb->data_len);
+	if (unlikely(skb->len < skb->data_len)) {
+#if defined(CONFIG_DEBUG_NET)
+		skb->len += len;
+		pr_err("__skb_pull(len=%u)\n", len);
+		skb_dump(KERN_ERR, skb, false);
+#endif
+		BUG();
+	}
 	return skb->data += len;
 }
 
-- 
2.36.1.255.ge46751e96f-goog

Re: [PATCH net 1/2] net: add debug info to __skb_pull()

[Willem de Bruijn]

On Tue, May 31, 2022 at 2:59 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> From: Eric Dumazet <edumazet@google.com>
>
> While analyzing yet another syzbot report, I found the following
> patch very useful. It allows to better understand what went wrong.
>
> This debug info is only enabled if CONFIG_DEBUG_NET=y,
> which is the case for syzbot builds.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Acked-by: Willem de Bruijn <willemb@google.com>

The skb_dump output (including packet headers) on these bugs will make
root causing these failures a lot easier in the future. Thanks!

Re: [PATCH net 1/2] net: add debug info to __skb_pull()

[kernel test robot]

Hi Eric,

I love your patch! Yet something to improve:

[auto build test ERROR on net/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git 09e545f7381459c015b6fa0cd0ac6f010ef8cc25
config: arc-randconfig-r021-20220531 (https://download.01.org/0day-ci/archive/20220601/202206011509.Rpp82wrl-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 11.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/a907c048e7699133feedaa06948c15c719a59f94
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
        git checkout a907c048e7699133feedaa06948c15c719a59f94
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   arc-elf-ld: kernel/bpf/cgroup.o: in function `__skb_pull':
   include/linux/skbuff.h:2703: undefined reference to `skb_dump'
>> arc-elf-ld: include/linux/skbuff.h:2703: undefined reference to `skb_dump'

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

Re: [PATCH net 1/2] net: add debug info to __skb_pull()

[Eric Dumazet]

On Wed, Jun 1, 2022 at 12:28 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Eric,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on net/master]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git 09e545f7381459c015b6fa0cd0ac6f010ef8cc25
> config: arc-randconfig-r021-20220531 (https://download.01.org/0day-ci/archive/20220601/202206011509.Rpp82wrl-lkp@intel.com/config)
> compiler: arc-elf-gcc (GCC) 11.3.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://github.com/intel-lab-lkp/linux/commit/a907c048e7699133feedaa06948c15c719a59f94
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
>         git checkout a907c048e7699133feedaa06948c15c719a59f94
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>    arc-elf-ld: kernel/bpf/cgroup.o: in function `__skb_pull':
>    include/linux/skbuff.h:2703: undefined reference to `skb_dump'
> >> arc-elf-ld: include/linux/skbuff.h:2703: undefined reference to `skb_dump'
>


So... CONFIG_NET=n  and yet __cgroup_bpf_run_filter_skb() is using skbs ?

Not sure if this makes any sense.



>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp

Re: [PATCH net 1/2] net: add debug info to __skb_pull()

[Eric Dumazet]

[-- Attachment #1: Type: text/plain, Size: 1948 bytes --]

On Wed, Jun 1, 2022 at 12:28 AM kernel test robot <lkp@intel.com> wrote:
>
> Hi Eric,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on net/master]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git 09e545f7381459c015b6fa0cd0ac6f010ef8cc25
> config: arc-randconfig-r021-20220531 (https://download.01.org/0day-ci/archive/20220601/202206011509.Rpp82wrl-lkp(a)intel.com/config)
> compiler: arc-elf-gcc (GCC) 11.3.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://github.com/intel-lab-lkp/linux/commit/a907c048e7699133feedaa06948c15c719a59f94
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
>         git checkout a907c048e7699133feedaa06948c15c719a59f94
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>    arc-elf-ld: kernel/bpf/cgroup.o: in function `__skb_pull':
>    include/linux/skbuff.h:2703: undefined reference to `skb_dump'
> >> arc-elf-ld: include/linux/skbuff.h:2703: undefined reference to `skb_dump'
>


So... CONFIG_NET=n  and yet __cgroup_bpf_run_filter_skb() is using skbs ?

Not sure if this makes any sense.



>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp

Re: [PATCH net 1/2] net: add debug info to __skb_pull()

[kernel test robot]

Hi Eric,

I love your patch! Yet something to improve:

[auto build test ERROR on net/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git 09e545f7381459c015b6fa0cd0ac6f010ef8cc25
config: hexagon-randconfig-r002-20220531 (https://download.01.org/0day-ci/archive/20220602/202206020557.QyvlGs0H-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project c825abd6b0198fb088d9752f556a70705bc99dfd)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/a907c048e7699133feedaa06948c15c719a59f94
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Eric-Dumazet/net-af_packet-be-careful-when-expanding-mac-header-size/20220601-030146
        git checkout a907c048e7699133feedaa06948c15c719a59f94
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> ld.lld: error: undefined symbol: skb_dump
   >>> referenced by cgroup.c
   >>>               bpf/cgroup.o:(__cgroup_bpf_run_filter_skb) in archive kernel/built-in.a
   >>> referenced by cgroup.c
   >>>               bpf/cgroup.o:(__cgroup_bpf_run_filter_skb) in archive kernel/built-in.a

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

[PATCH net 2/2] net/af_packet: make sure to pull mac header

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

GSO assumes skb->head contains link layer headers.

tun device in some case can provide base 14 bytes,
regardless of VLAN being used or not.

After blamed commit, we can end up setting a network
header offset of 18+, we better pull the missing
bytes to avoid a posible crash in GSO.

syzbot report was:
kernel BUG at include/linux/skbuff.h:2699!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 3601 Comm: syz-executor210 Not tainted 5.18.0-syzkaller-11338-g2c5ca23f7414 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__skb_pull include/linux/skbuff.h:2699 [inline]
RIP: 0010:skb_mac_gso_segment+0x48f/0x530 net/core/gro.c:136
Code: 00 48 c7 c7 00 96 d4 8a c6 05 cb d3 45 06 01 e8 26 bb d0 01 e9 2f fd ff ff 49 c7 c4 ea ff ff ff e9 f1 fe ff ff e8 91 84 19 fa <0f> 0b 48 89 df e8 97 44 66 fa e9 7f fd ff ff e8 ad 44 66 fa e9 48
RSP: 0018:ffffc90002e2f4b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000012 RCX: 0000000000000000
RDX: ffff88805bb58000 RSI: ffffffff8760ed0f RDI: 0000000000000004
RBP: 0000000000005dbc R08: 0000000000000004 R09: 0000000000000fe0
R10: 0000000000000fe4 R11: 0000000000000000 R12: 0000000000000fe0
R13: ffff88807194d780 R14: 1ffff920005c5e9b R15: 0000000000000012
FS:  000055555730f300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200015c0 CR3: 0000000071ff8000 CR4: 0000000000350ee0
Call Trace:
 <TASK>
 __skb_gso_segment+0x327/0x6e0 net/core/dev.c:3411
 skb_gso_segment include/linux/netdevice.h:4749 [inline]
 validate_xmit_skb+0x6bc/0xf10 net/core/dev.c:3669
 validate_xmit_skb_list+0xbc/0x120 net/core/dev.c:3719
 sch_direct_xmit+0x3d1/0xbe0 net/sched/sch_generic.c:327
 __dev_xmit_skb net/core/dev.c:3815 [inline]
 __dev_queue_xmit+0x14a1/0x3a00 net/core/dev.c:4219
 packet_snd net/packet/af_packet.c:3071 [inline]
 packet_sendmsg+0x21cb/0x5550 net/packet/af_packet.c:3102
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:734
 ____sys_sendmsg+0x6eb/0x810 net/socket.c:2492
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2546
 __sys_sendmsg net/socket.c:2575 [inline]
 __do_sys_sendmsg net/socket.c:2584 [inline]
 __se_sys_sendmsg net/socket.c:2582 [inline]
 __x64_sys_sendmsg+0x132/0x220 net/socket.c:2582
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f4b95da06c9
Code: 28 c3 e8 4a 15 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd7defc4c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ffd7defc4f0 RCX: 00007f4b95da06c9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 0000000000000003 R08: bb1414ac00000050 R09: bb1414ac00000050
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd7defc4e0 R14: 00007ffd7defc4d8 R15: 00007ffd7defc4d4
 </TASK>

Fixes: dfed913e8b55 ("net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Hangbin Liu <liuhangbin@gmail.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
---
 net/packet/af_packet.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 677f9cfa9660816a160a11bfa4c291431412005f..ca6e92a229239f9093900bf9249396cf0d410104 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1935,8 +1935,10 @@ static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
 	/* Move network header to the right position for VLAN tagged packets */
 	if (likely(skb->dev->type == ARPHRD_ETHER) &&
 	    eth_type_vlan(skb->protocol) &&
-	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
-		skb_set_network_header(skb, depth);
+	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0) {
+		if (pskb_may_pull(skb, depth))
+			skb_set_network_header(skb, depth);
+	}
 
 	skb_probe_transport_header(skb);
 }
-- 
2.36.1.255.ge46751e96f-goog

Re: [PATCH net 2/2] net/af_packet: make sure to pull mac header

[Willem de Bruijn]

On Tue, May 31, 2022 at 2:59 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> From: Eric Dumazet <edumazet@google.com>
>
> GSO assumes skb->head contains link layer headers.
>
> tun device in some case can provide base 14 bytes,
> regardless of VLAN being used or not.
>
> After blamed commit, we can end up setting a network
> header offset of 18+, we better pull the missing
> bytes to avoid a posible crash in GSO.
>
> syzbot report was:
> kernel BUG at include/linux/skbuff.h:2699!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 3601 Comm: syz-executor210 Not tainted 5.18.0-syzkaller-11338-g2c5ca23f7414 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__skb_pull include/linux/skbuff.h:2699 [inline]
> RIP: 0010:skb_mac_gso_segment+0x48f/0x530 net/core/gro.c:136
> Code: 00 48 c7 c7 00 96 d4 8a c6 05 cb d3 45 06 01 e8 26 bb d0 01 e9 2f fd ff ff 49 c7 c4 ea ff ff ff e9 f1 fe ff ff e8 91 84 19 fa <0f> 0b 48 89 df e8 97 44 66 fa e9 7f fd ff ff e8 ad 44 66 fa e9 48
> RSP: 0018:ffffc90002e2f4b8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000012 RCX: 0000000000000000
> RDX: ffff88805bb58000 RSI: ffffffff8760ed0f RDI: 0000000000000004
> RBP: 0000000000005dbc R08: 0000000000000004 R09: 0000000000000fe0
> R10: 0000000000000fe4 R11: 0000000000000000 R12: 0000000000000fe0
> R13: ffff88807194d780 R14: 1ffff920005c5e9b R15: 0000000000000012
> FS:  000055555730f300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200015c0 CR3: 0000000071ff8000 CR4: 0000000000350ee0
> Call Trace:
>  <TASK>
>  __skb_gso_segment+0x327/0x6e0 net/core/dev.c:3411
>  skb_gso_segment include/linux/netdevice.h:4749 [inline]
>  validate_xmit_skb+0x6bc/0xf10 net/core/dev.c:3669
>  validate_xmit_skb_list+0xbc/0x120 net/core/dev.c:3719
>  sch_direct_xmit+0x3d1/0xbe0 net/sched/sch_generic.c:327
>  __dev_xmit_skb net/core/dev.c:3815 [inline]
>  __dev_queue_xmit+0x14a1/0x3a00 net/core/dev.c:4219
>  packet_snd net/packet/af_packet.c:3071 [inline]
>  packet_sendmsg+0x21cb/0x5550 net/packet/af_packet.c:3102
>  sock_sendmsg_nosec net/socket.c:714 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:734
>  ____sys_sendmsg+0x6eb/0x810 net/socket.c:2492
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2546
>  __sys_sendmsg net/socket.c:2575 [inline]
>  __do_sys_sendmsg net/socket.c:2584 [inline]
>  __se_sys_sendmsg net/socket.c:2582 [inline]
>  __x64_sys_sendmsg+0x132/0x220 net/socket.c:2582
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
> RIP: 0033:0x7f4b95da06c9
> Code: 28 c3 e8 4a 15 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd7defc4c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007ffd7defc4f0 RCX: 00007f4b95da06c9
> RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
> RBP: 0000000000000003 R08: bb1414ac00000050 R09: bb1414ac00000050
> R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffd7defc4e0 R14: 00007ffd7defc4d8 R15: 00007ffd7defc4d4
>  </TASK>
>
> Fixes: dfed913e8b55 ("net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Cc: Hangbin Liu <liuhangbin@gmail.com>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>

Acked-by: Willem de Bruijn <willemb@google.com>

Thanks for fixing this, Eric.

Re: [PATCH net 2/2] net/af_packet: make sure to pull mac header

[Hangbin Liu]

Hi Eric,

On Tue, May 31, 2022 at 11:59:33AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> GSO assumes skb->head contains link layer headers.
> 
> tun device in some case can provide base 14 bytes,
> regardless of VLAN being used or not.
> 
> After blamed commit, we can end up setting a network
> header offset of 18+, we better pull the missing
> bytes to avoid a posible crash in GSO.
> 
> syzbot report was:
> kernel BUG at include/linux/skbuff.h:2699!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 3601 Comm: syz-executor210 Not tainted 5.18.0-syzkaller-11338-g2c5ca23f7414 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__skb_pull include/linux/skbuff.h:2699 [inline]
> RIP: 0010:skb_mac_gso_segment+0x48f/0x530 net/core/gro.c:136
> Code: 00 48 c7 c7 00 96 d4 8a c6 05 cb d3 45 06 01 e8 26 bb d0 01 e9 2f fd ff ff 49 c7 c4 ea ff ff ff e9 f1 fe ff ff e8 91 84 19 fa <0f> 0b 48 89 df e8 97 44 66 fa e9 7f fd ff ff e8 ad 44 66 fa e9 48
> RSP: 0018:ffffc90002e2f4b8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000012 RCX: 0000000000000000
> RDX: ffff88805bb58000 RSI: ffffffff8760ed0f RDI: 0000000000000004
> RBP: 0000000000005dbc R08: 0000000000000004 R09: 0000000000000fe0
> R10: 0000000000000fe4 R11: 0000000000000000 R12: 0000000000000fe0
> R13: ffff88807194d780 R14: 1ffff920005c5e9b R15: 0000000000000012
> FS:  000055555730f300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200015c0 CR3: 0000000071ff8000 CR4: 0000000000350ee0
> Call Trace:
>  <TASK>
>  __skb_gso_segment+0x327/0x6e0 net/core/dev.c:3411
>  skb_gso_segment include/linux/netdevice.h:4749 [inline]
>  validate_xmit_skb+0x6bc/0xf10 net/core/dev.c:3669
>  validate_xmit_skb_list+0xbc/0x120 net/core/dev.c:3719
>  sch_direct_xmit+0x3d1/0xbe0 net/sched/sch_generic.c:327
>  __dev_xmit_skb net/core/dev.c:3815 [inline]
>  __dev_queue_xmit+0x14a1/0x3a00 net/core/dev.c:4219
>  packet_snd net/packet/af_packet.c:3071 [inline]
>  packet_sendmsg+0x21cb/0x5550 net/packet/af_packet.c:3102
>  sock_sendmsg_nosec net/socket.c:714 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:734
>  ____sys_sendmsg+0x6eb/0x810 net/socket.c:2492
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2546
>  __sys_sendmsg net/socket.c:2575 [inline]
>  __do_sys_sendmsg net/socket.c:2584 [inline]
>  __se_sys_sendmsg net/socket.c:2582 [inline]
>  __x64_sys_sendmsg+0x132/0x220 net/socket.c:2582
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
> RIP: 0033:0x7f4b95da06c9
> Code: 28 c3 e8 4a 15 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd7defc4c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007ffd7defc4f0 RCX: 00007f4b95da06c9
> RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
> RBP: 0000000000000003 R08: bb1414ac00000050 R09: bb1414ac00000050
> R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffd7defc4e0 R14: 00007ffd7defc4d8 R15: 00007ffd7defc4d4
>  </TASK>
> 
> Fixes: dfed913e8b55 ("net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Cc: Hangbin Liu <liuhangbin@gmail.com>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> ---
>  net/packet/af_packet.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 677f9cfa9660816a160a11bfa4c291431412005f..ca6e92a229239f9093900bf9249396cf0d410104 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -1935,8 +1935,10 @@ static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
>  	/* Move network header to the right position for VLAN tagged packets */
>  	if (likely(skb->dev->type == ARPHRD_ETHER) &&
>  	    eth_type_vlan(skb->protocol) &&
> -	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
> -		skb_set_network_header(skb, depth);
> +	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0) {
> +		if (pskb_may_pull(skb, depth))
> +			skb_set_network_header(skb, depth);
> +	}
>  
>  	skb_probe_transport_header(skb);
>  }
> -- 
> 2.36.1.255.ge46751e96f-goog
> 

Thanks for the fix!

Acked-by: Hangbin Liu <liuhangbin@gmail.com>