Revert "tcp: Reset tcp connections in SYN-SENT state"

This reverts commit e880f8b3.

1) Patch has not been properly tested, and is wrong [1]
2) Patch submission did not include TCP maintainer (this is me)

[1]
divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8426 Comm: syz-executor478 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__tcp_select_window+0x56d/0xad0 net/ipv4/tcp_output.c:3015
Code: 44 89 ff e8 d5 cd f0 f9 45 39 e7 0f 8d 20 ff ff ff e8 f7 c7 f0 f9 44 89 e3 e9 13 ff ff ff e8 ea c7 f0 f9 44 89 e0 44 89 e3 99 <f7> 7c 24 04 29 d3 e9 fc fe ff ff e8 d3 c7 f0 f9 41 f7 dc bf 1f 00
RSP: 0018:ffffc9000184fac0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff87832e76 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff87832e14 R11: 0000000000000000 R12: 0000000000000000
R13: 1ffff92000309f5c R14: 0000000000000000 R15: 0000000000000000
FS:  00000000023eb300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc2b5f426c0 CR3: 000000001c5cf000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tcp_select_window net/ipv4/tcp_output.c:264 [inline]
 __tcp_transmit_skb+0xa82/0x38f0 net/ipv4/tcp_output.c:1351
 tcp_transmit_skb net/ipv4/tcp_output.c:1423 [inline]
 tcp_send_active_reset+0x475/0x8e0 net/ipv4/tcp_output.c:3449
 tcp_disconnect+0x15a9/0x1e60 net/ipv4/tcp.c:2955
 inet_shutdown+0x260/0x430 net/ipv4/af_inet.c:905
 __sys_shutdown_sock net/socket.c:2189 [inline]
 __sys_shutdown_sock net/socket.c:2183 [inline]
 __sys_shutdown+0xf1/0x1b0 net/socket.c:2201
 __do_sys_shutdown net/socket.c:2209 [inline]
 __se_sys_shutdown net/socket.c:2207 [inline]
 __x64_sys_shutdown+0x50/0x70 net/socket.c:2207
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: e880f8b3 ("tcp: Reset tcp connections in SYN-SENT state")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Manoj Basapathi <manojbm@codeaurora.org>
Cc: Sauvik Saha <ssaha@codeaurora.org>
Link: https://lore.kernel.org/r/20210409170237.274904-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/tcp.c

@@ -2888,7 +2888,7 @@ static inline bool tcp_need_reset(int state)
 {
 	return (1 << state) &
 	       (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT | TCPF_FIN_WAIT1 |
-		TCPF_FIN_WAIT2 | TCPF_SYN_RECV | TCPF_SYN_SENT);
+		TCPF_FIN_WAIT2 | TCPF_SYN_RECV);
 }
 
 static void tcp_rtx_queue_purge(struct sock *sk)
@@ -2954,7 +2954,8 @@ int tcp_disconnect(struct sock *sk, int flags)
 		 */
 		tcp_send_active_reset(sk, gfp_any());
 		sk->sk_err = ECONNRESET;
-	}
+	} else if (old_state == TCP_SYN_SENT)
+		sk->sk_err = ECONNRESET;
 
 	tcp_clear_xmit_timers(sk);
 	__skb_queue_purge(&sk->sk_receive_queue);