CVE-2022-49663

In the Linux kernel, the following vulnerability has been resolved:

tunnels: do not assume mac header is set in skbtunnelcheck_pmtu()

Recently added debug in commit f9aefd6b2aa3 ("net: warn if mac header was not set") caught a bug in skbtunnelcheck_pmtu(), as shown in this syzbot report [1].

In ndostartxmit() paths, there is really no need to use skb->mac_header, because skb->data is supposed to point at it.

[1] WARNING: CPU: 1 PID: 8604 at include/linux/skbuff.h:2784 skbmacheaderlen include/linux/skbuff.h:2784 [inline] WARNING: CPU: 1 PID: 8604 at include/linux/skbuff.h:2784 skbtunnelcheckpmtu+0x5de/0x2f90 net/ipv4/iptunnelcore.c:413 Modules linked in: CPU: 1 PID: 8604 Comm: syz-executor.3 Not tainted 5.19.0-rc2-syzkaller-00443-g8720bd951b8e #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:skbmacheaderlen include/linux/skbuff.h:2784 [inline] RIP: 0010:skbtunnelcheckpmtu+0x5de/0x2f90 net/ipv4/iptunnelcore.c:413 Code: 00 00 00 00 fc ff df 4c 89 fa 48 c1 ea 03 80 3c 02 00 0f 84 b9 fe ff ff 4c 89 ff e8 7c 0f d7 f9 e9 ac fe ff ff e8 c2 13 8a f9 <0f> 0b e9 28 fc ff ff e8 b6 13 8a f9 48 8b 54 24 70 48 b8 00 00 00 RSP: 0018:ffffc90002e4f520 EFLAGS: 00010212 RAX: 0000000000000324 RBX: ffff88804d5fd500 RCX: ffffc90005b52000 RDX: 0000000000040000 RSI: ffffffff87f05e3e RDI: 0000000000000003 RBP: ffffc90002e4f650 R08: 0000000000000003 R09: 000000000000ffff R10: 000000000000ffff R11: 0000000000000000 R12: 000000000000ffff R13: 0000000000000000 R14: 000000000000ffcd R15: 000000000000001f FS: 00007f3babba9700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000080 CR3: 0000000075319000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> genevexmitskb drivers/net/geneve.c:927 [inline] genevexmit+0xcf8/0x35d0 drivers/net/geneve.c:1107 netdevstartxmit include/linux/netdevice.h:4805 [inline] netdevstartxmit include/linux/netdevice.h:4819 [inline] _devdirectxmit+0x500/0x730 net/core/dev.c:4309 devdirectxmit include/linux/netdevice.h:3007 [inline] packetdirectxmit+0x1b8/0x2c0 net/packet/afpacket.c:282 packetsnd net/packet/afpacket.c:3073 [inline] packetsendmsg+0x21f4/0x55d0 net/packet/afpacket.c:3104 socksendmsgnosec net/socket.c:714 [inline] socksendmsg+0xcf/0x120 net/socket.c:734 syssendmsg+0x6eb/0x810 net/socket.c:2489 _syssendmsg+0xf3/0x170 net/socket.c:2543 _syssendmsg net/socket.c:2572 [inline] _dosyssendmsg net/socket.c:2581 [inline] _sesyssendmsg net/socket.c:2579 [inline] _x64syssendmsg+0x132/0x220 net/socket.c:2579 dosyscallx64 arch/x86/entry/common.c:50 [inline] dosyscall64+0x35/0xb0 arch/x86/entry/common.c:80 entrySYSCALL64afterhwframe+0x46/0xb0 RIP: 0033:0x7f3baaa89109 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3babba9168 EFLAGS: 00000246 ORIGRAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f3baab9bf60 RCX: 00007f3baaa89109 RDX: 0000000000000000 RSI: 0000000020000a00 RDI: 0000000000000003 RBP: 00007f3baaae305d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe74f2543f R14: 00007f3babba9300 R15: 0000000000022000 </TASK>