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TCP recvmsg seq # bug 2: copied 23813075, seq 236D3464, rcvnxt 237033C5, fl 40
WARNING: CPU: 3 PID: 6398 at net/ipv4/tcp.c:2721 tcp_recvmsg_locked+0xb2f/0x2910 net/ipv4/tcp.c:2721
Modules linked in:
CPU: 3 UID: 0 PID: 6398 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~bpo12+1 04/01/2014
RIP: 0010:tcp_recvmsg_locked+0xb2f/0x2910 net/ipv4/tcp.c:2721
Code: 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 b8 1c 00 00 48 8b 04 24 44 8b 44 24 30 89 da 48 c7 c7 00 a1 ab 8c 8b 30 e8 92 86 b9 f7 90 <0f> 0b 90 90 e9 ad f9 ff ff e8 53 00 fb f7 49 8d 5c 24 60 be 08 00
RSP: 0018:ffffc900016ff488 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 00000000236d3464 RCX: ffffffff8179bd78
RDX: ffff888022358000 RSI: ffffffff8179bd85 RDI: 0000000000000001
RBP: ffff88802e3ea8f4 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88802e3ea8e8
R13: ffff88802e3ea8c0 R14: 000000000000ffcb R15: dffffc0000000000
FS:  00007f4391dfe6c0(0000) GS:ffff8880d7185000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4391dfdf98 CR3: 0000000024b62000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 receive_fallback_to_copy net/ipv4/tcp.c:1965 [inline]
 tcp_zerocopy_receive+0x131a/0x2120 net/ipv4/tcp.c:2197
 do_tcp_getsockopt+0xe28/0x26c0 net/ipv4/tcp.c:4710
 tcp_getsockopt+0xdf/0x100 net/ipv4/tcp.c:4809
 do_sock_getsockopt+0x34d/0x440 net/socket.c:2421
 __sys_getsockopt+0x12f/0x260 net/socket.c:2450
 __do_sys_getsockopt net/socket.c:2457 [inline]
 __se_sys_getsockopt net/socket.c:2454 [inline]
 __x64_sys_getsockopt+0xbd/0x160 net/socket.c:2454
 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: 0033:0x7f4392b8cde9
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4391dfe038 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007f4392da6080 RCX: 00007f4392b8cde9
RDX: 0000000000000023 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007f4392c0e2a0 R08: 0000400000000380 R09: 0000000000000000
R10: 0000400000000340 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f4392da6080 R15: 00007ffe17e40538
 </TASK>