netdev - Re: [PATCH net] net: add vlan_get_protocol_and

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Date: Wed, 10 May 2023 10:00:56 +0200
From: Simon Horman <simon.horman@...igine.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, eric.dumazet@...il.com,
	syzbot <syzkaller@...glegroups.com>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net] net: add vlan_get_protocol_and_depth() helper

On Tue, May 09, 2023 at 01:18:57PM +0000, Eric Dumazet wrote:
> Before blamed commit, pskb_may_pull() was used instead
> of skb_header_pointer() in __vlan_get_protocol() and friends.
> 
> Few callers depended on skb->head being populated with MAC header,
> syzbot caught one of them (skb_mac_gso_segment())
> 
> Add vlan_get_protocol_and_depth() to make the intent clearer
> and use it where sensible.
> 
> This is a more generic fix than commit e9d3f80935b6
> ("net/af_packet: make sure to pull mac header") which was
> dealing with a similar issue.
> 
> kernel BUG at include/linux/skbuff.h:2655 !
> invalid opcode: 0000 [#1] SMP KASAN
> CPU: 0 PID: 1441 Comm: syz-executor199 Not tainted 6.1.24-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
> RIP: 0010:__skb_pull include/linux/skbuff.h:2655 [inline]
> RIP: 0010:skb_mac_gso_segment+0x68f/0x6a0 net/core/gro.c:136
> Code: fd 48 8b 5c 24 10 44 89 6b 70 48 c7 c7 c0 ae 0d 86 44 89 e6 e8 a1 91 d0 00 48 c7 c7 00 af 0d 86 48 89 de 31 d2 e8 d1 4a e9 ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
> RSP: 0018:ffffc90001bd7520 EFLAGS: 00010286
> RAX: ffffffff8469736a RBX: ffff88810f31dac0 RCX: ffff888115a18b00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90001bd75e8 R08: ffffffff84697183 R09: fffff5200037adf9
> R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000012
> R13: 000000000000fee5 R14: 0000000000005865 R15: 000000000000fed7
> FS: 000055555633f300(0000) GS:ffff8881f6a00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000000 CR3: 0000000116fea000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> [<ffffffff847018dd>] __skb_gso_segment+0x32d/0x4c0 net/core/dev.c:3419
> [<ffffffff8470398a>] skb_gso_segment include/linux/netdevice.h:4819 [inline]
> [<ffffffff8470398a>] validate_xmit_skb+0x3aa/0xee0 net/core/dev.c:3725
> [<ffffffff84707042>] __dev_queue_xmit+0x1332/0x3300 net/core/dev.c:4313
> [<ffffffff851a9ec7>] dev_queue_xmit+0x17/0x20 include/linux/netdevice.h:3029
> [<ffffffff851b4a82>] packet_snd net/packet/af_packet.c:3111 [inline]
> [<ffffffff851b4a82>] packet_sendmsg+0x49d2/0x6470 net/packet/af_packet.c:3142
> [<ffffffff84669a12>] sock_sendmsg_nosec net/socket.c:716 [inline]
> [<ffffffff84669a12>] sock_sendmsg net/socket.c:736 [inline]
> [<ffffffff84669a12>] __sys_sendto+0x472/0x5f0 net/socket.c:2139
> [<ffffffff84669c75>] __do_sys_sendto net/socket.c:2151 [inline]
> [<ffffffff84669c75>] __se_sys_sendto net/socket.c:2147 [inline]
> [<ffffffff84669c75>] __x64_sys_sendto+0xe5/0x100 net/socket.c:2147
> [<ffffffff8551d40f>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> [<ffffffff8551d40f>] do_syscall_64+0x2f/0x50 arch/x86/entry/common.c:80
> [<ffffffff85600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: 469aceddfa3e ("vlan: consolidate VLAN parsing code and limit max parsing depth")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Toke Høiland-Jørgensen <toke@...hat.com>
> Cc: Willem de Bruijn <willemb@...gle.com>

Reviewed-by: Simon Horman <simon.horman@...igine.com>