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TCP recvmsg seq # bug 2: copied B856D6D4, seq B84EDEB1, rcvnxt B852DDDD, fl 40
WARNING: CPU: 1 PID: 6440 at net/ipv4/tcp.c:2701 tcp_recvmsg_locked+0xb53/0x2870 net/ipv4/tcp.c:2701
Modules linked in:
CPU: 1 UID: 0 PID: 6440 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+0xb53/0x2870 net/ipv4/tcp.c:2701
Code: 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 15 1b 00 00 48 8b 04 24 44 8b 44 24 30 89 da 48 c7 c7 80 c3 f1 8c 8b 30 e8 0e d2 78 f7 90 <0f> 0b 90 90 e9 e1 f9 ff ff e8 8f 2d ba f7 49 8d 5c 24 60 be 08 00
RSP: 0018:ffffc900043cf4a8 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 00000000b84edeb1 RCX: ffffffff817a4388
RDX: ffff888027ac0000 RSI: ffffffff817a4395 RDI: 0000000000000001
RBP: ffff8880327df6b4 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880327df6a8
R13: ffff8880327df680 R14: 000000000003ff2c R15: dffffc0000000000
FS:  00007fe5cb2576c0(0000) GS:ffff8880d67b2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000208d6000 CR3: 000000002b931000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 receive_fallback_to_copy net/ipv4/tcp.c:1945 [inline]
 tcp_zerocopy_receive+0x12db/0x20f0 net/ipv4/tcp.c:2177
 do_tcp_getsockopt+0x10ee/0x2670 net/ipv4/tcp.c:4670
 tcp_getsockopt+0xdf/0x100 net/ipv4/tcp.c:4769
 do_sock_getsockopt+0x34a/0x440 net/socket.c:2405
 __sys_getsockopt+0x12f/0x260 net/socket.c:2434
 __do_sys_getsockopt net/socket.c:2441 [inline]
 __se_sys_getsockopt net/socket.c:2438 [inline]
 __x64_sys_getsockopt+0xbd/0x160 net/socket.c:2438
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe5ca47cee9
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:00007fe5cb2570c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007fe5ca5ac050 RCX: 00007fe5ca47cee9
RDX: 0000000000000023 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007fe5ca4c949e R08: 0000000020000380 R09: 0000000000000000
R10: 0000000020000340 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007fe5ca5ac050 R15: 00007ffeaa9325d8
 </TASK>