------------[ cut here ]------------
TCP recvmsg seq # bug 2: copied D6A70E34, seq D645227E, rcvnxt D6601B73, fl 40
WARNING: net/ipv4/tcp.c:2775 at tcp_recvmsg_locked+0xa7f/0x28e0 net/ipv4/tcp.c:2775, CPU#2: syz.0.16/6376
Modules linked in:
CPU: 2 UID: 0 PID: 6376 Comm: syz.0.16 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:tcp_recvmsg_locked+0xa8c/0x28e0 net/ipv4/tcp.c:2775
Code: 20 48 89 f0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 be 1d 00 00 48 8d 3d e1 6e f3 06 48 8b 04 24 44 8b 44 24 2c 89 da 8b 30 <67> 48 0f b9 3a e9 0e fa ff ff e8 05 d6 13 f8 49 8d 5e 60 be 08 00
RSP: 0018:ffffc9000422f450 EFLAGS: 00010246
RAX: ffff88802c55a280 RBX: 00000000d645227e RCX: 00000000d6601b73
RDX: 00000000d645227e RSI: 00000000d6a70e34 RDI: ffffffff90e83780
RBP: 000000000000ffcb R08: 0000000000000040 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff888037cd5a40 R14: ffff888037cd5a68 R15: ffff888037cd5a74
FS:  00007fc5925e86c0(0000) GS:ffff8880d6547000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000400000b96000 CR3: 0000000048e86000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 receive_fallback_to_copy net/ipv4/tcp.c:2021 [inline]
 tcp_zerocopy_receive+0x14cc/0x2640 net/ipv4/tcp.c:2253
 do_tcp_getsockopt+0xc05/0x2a90 net/ipv4/tcp.c:4796
 tcp_getsockopt+0xe4/0x110 net/ipv4/tcp.c:4895
 do_sock_getsockopt+0x259/0x3d0 net/socket.c:2383
 __sys_getsockopt+0x148/0x260 net/socket.c:2412
 __do_sys_getsockopt net/socket.c:2419 [inline]
 __se_sys_getsockopt net/socket.c:2416 [inline]
 __x64_sys_getsockopt+0xbd/0x160 net/socket.c:2416
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc591797479
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc5925e8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007fc5919c6080 RCX: 00007fc591797479
RDX: 0000000000000023 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007fc5918281bc R08: 0000400000000380 R09: 0000000000000000
R10: 0000400000000340 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fc5919c6080 R15: 00007ffec58e12a8
 </TASK>
----------------
Code disassembly (best guess):
   0:	20 48 89             	and    %cl,-0x77(%rax)
   3:	f0 83 e0 07          	lock and $0x7,%eax
   7:	83 c0 03             	add    $0x3,%eax
   a:	38 d0                	cmp    %dl,%al
   c:	7c 08                	jl     0x16
   e:	84 d2                	test   %dl,%dl
  10:	0f 85 be 1d 00 00    	jne    0x1dd4
  16:	48 8d 3d e1 6e f3 06 	lea    0x6f36ee1(%rip),%rdi        # 0x6f36efe
  1d:	48 8b 04 24          	mov    (%rsp),%rax
  21:	44 8b 44 24 2c       	mov    0x2c(%rsp),%r8d
  26:	89 da                	mov    %ebx,%edx
  28:	8b 30                	mov    (%rax),%esi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 0e fa ff ff       	jmp    0xfffffa42
  34:	e8 05 d6 13 f8       	call   0xf813d63e
  39:	49 8d 5e 60          	lea    0x60(%r14),%rbx
  3d:	be                   	.byte 0xbe
  3e:	08 00                	or     %al,(%rax)