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TCP recvmsg seq # bug 2: copied 967ED30B, seq 962AE46F, rcvnxt 9639DFC8, fl 40
WARNING: net/ipv4/tcp.c:2725 at 0x0, CPU#1: syz-executor/6399
Modules linked in:
CPU: 1 UID: 0 PID: 6399 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:tcp_recvmsg_locked+0xb22/0x2910 net/ipv4/tcp.c:2725
Code: 38 48 89 f0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 b3 1c 00 00 48 8d 3d ab 09 c8 06 48 8b 04 24 44 8b 44 24 30 89 da 8b 30 <67> 48 0f b9 3a e9 b9 f9 ff ff e8 3f 7f f1 f7 49 8d 5c 24 60 be 08
RSP: 0018:ffffc900049bf468 EFLAGS: 00010246
RAX: ffff88803252bbf0 RBX: 00000000962ae46f RCX: 000000009639dfc8
RDX: 00000000962ae46f RSI: 00000000967ed30b RDI: ffffffff9094b090
RBP: ffff88803b820f34 R08: 0000000000000040 R09: 0000000000000000
R10: 0000000000000000 R11: 000000009dea9dbf R12: ffff88803b820f28
R13: ffff88803b820f00 R14: 000000000000ffcb R15: dffffc0000000000
FS:  00007ff394caa6c0(0000) GS:ffff8880d6a60000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff394caad58 CR3: 000000004797a000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 receive_fallback_to_copy net/ipv4/tcp.c:1969 [inline]
 tcp_zerocopy_receive+0x131a/0x2120 net/ipv4/tcp.c:2201
 do_tcp_getsockopt+0xdf9/0x2b20 net/ipv4/tcp.c:4737
 tcp_getsockopt+0xdf/0x100 net/ipv4/tcp.c:4836
 do_sock_getsockopt+0x324/0x410 net/socket.c:2374
 __sys_getsockopt+0x12f/0x260 net/socket.c:2403
 __do_sys_getsockopt net/socket.c:2410 [inline]
 __se_sys_getsockopt net/socket.c:2407 [inline]
 __x64_sys_getsockopt+0xbd/0x160 net/socket.c:2407
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff393e7cee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff394caa0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007ff393fac050 RCX: 00007ff393e7cee9
RDX: 0000000000000023 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007ff393ec949e R08: 0000000020000380 R09: 0000000000000000
R10: 0000000020000340 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007ff393fac050 R15: 00007fffca17a598
 </TASK>
----------------
Code disassembly (best guess):
   0:	38 48 89             	cmp    %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 b3 1c 00 00    	jne    0x1cc9
  16:	48 8d 3d ab 09 c8 06 	lea    0x6c809ab(%rip),%rdi        # 0x6c809c8
  1d:	48 8b 04 24          	mov    (%rsp),%rax
  21:	44 8b 44 24 30       	mov    0x30(%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 b9 f9 ff ff       	jmp    0xfffff9ed
  34:	e8 3f 7f f1 f7       	call   0xf7f17f78
  39:	49 8d 5c 24 60       	lea    0x60(%r12),%rbx
  3e:	be                   	.byte 0xbe
  3f:	08                   	.byte 0x8