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TCP recvmsg seq # bug 2: copied 8F4976C3, seq 8F49768B, rcvnxt 8F49768C, fl 40
WARNING: net/ipv4/tcp.c:2778 at tcp_recvmsg_locked+0x7d2/0x36b0 net/ipv4/tcp.c:2776, CPU#1: syz.0.48/6634
Modules linked in:
CPU: 1 UID: 0 PID: 6634 Comm: syz.0.48 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:tcp_recvmsg_locked+0x826/0x36b0 net/ipv4/tcp.c:2776
Code: 00 48 8b 54 24 68 0f 85 22 01 00 00 8b 12 4c 89 c0 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 42 01 00 00 41 8b 08 44 8b 44 24 40 <67> 48 0f b9 3a e9 3f ff ff ff 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c
RSP: 0018:ffffc900041df200 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000008f49768c
RDX: 000000008f49768b RSI: 000000008f4976c3 RDI: ffffffff8f78b700
RBP: ffffc900041df5f0 R08: 0000000000000040 R09: 0000000000000000
R10: ffffc900041df713 R11: fffff5200083bee4 R12: dffffc0000000000
R13: ffff888043e3a028 R14: 1ffff11007add793 R15: dffffc0000000000
FS:  00007ffa52c7e6c0(0000) GS:ffff888126432000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002000cf3d CR3: 0000000037954000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 receive_fallback_to_copy net/ipv4/tcp.c:2022 [inline]
 tcp_zerocopy_receive+0x7fe/0x20e0 net/ipv4/tcp.c:2254
 do_tcp_getsockopt+0x208a/0x2950 net/ipv4/tcp.c:4797
 tcp_getsockopt+0x83/0x130 net/ipv4/tcp.c:4896
 do_sock_getsockopt+0x2d3/0x3f0 net/socket.c:2383
 __sys_getsockopt net/socket.c:2412 [inline]
 __do_sys_getsockopt net/socket.c:2419 [inline]
 __se_sys_getsockopt net/socket.c:2416 [inline]
 __x64_sys_getsockopt+0x1aa/0x250 net/socket.c:2416
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ffa53a08569
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:00007ffa52c7e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007ffa53bd5fa0 RCX: 00007ffa53a08569
RDX: 0000000000000023 RSI: 0000000000000006 RDI: 0000000000000003
RBP: 00007ffa53a8b7af R08: 00000000200004c0 R09: 0000000000000000
R10: 0000000020000380 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffa53bd5fa0 R15: 00007ffc62837838
 </TASK>
----------------
Code disassembly (best guess):
   0:	00 48 8b             	add    %cl,-0x75(%rax)
   3:	54                   	push   %rsp
   4:	24 68                	and    $0x68,%al
   6:	0f 85 22 01 00 00    	jne    0x12e
   c:	8b 12                	mov    (%rdx),%edx
   e:	4c 89 c0             	mov    %r8,%rax
  11:	48 c1 e8 03          	shr    $0x3,%rax
  15:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax
  1a:	84 c0                	test   %al,%al
  1c:	0f 85 42 01 00 00    	jne    0x164
  22:	41 8b 08             	mov    (%r8),%ecx
  25:	44 8b 44 24 40       	mov    0x40(%rsp),%r8d
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 3f ff ff ff       	jmp    0xffffff73
  34:	89 f9                	mov    %edi,%ecx
  36:	80 e1 07             	and    $0x7,%cl
  39:	80 c1 03             	add    $0x3,%cl
  3c:	38 c1                	cmp    %al,%cl
  3e:	0f                   	.byte 0xf
  3f:	8c                   	.byte 0x8c