From d47a72152097d7be7cfc453d205196c0aa976c33 Mon Sep 17 00:00:00 2001 From: Davide Caratti Date: Mon, 6 Jul 2020 21:06:12 +0200 Subject: [PATCH] mptcp: fix race in subflow_data_ready() syzkaller was able to make the kernel reach subflow_data_ready() for a server subflow that was closed before subflow_finish_connect() completed. In these cases we can avoid using the path for regular/fallback MPTCP data, and just wake the main socket, to avoid the following warning: WARNING: CPU: 0 PID: 9370 at net/mptcp/subflow.c:885 subflow_data_ready+0x1e6/0x290 net/mptcp/subflow.c:885 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 9370 Comm: syz-executor.0 Not tainted 5.7.0 #106 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xb7/0xfe lib/dump_stack.c:118 panic+0x29e/0x692 kernel/panic.c:221 __warn.cold+0x2f/0x3d kernel/panic.c:582 report_bug+0x28b/0x2f0 lib/bug.c:195 fixup_bug arch/x86/kernel/traps.c:105 [inline] fixup_bug arch/x86/kernel/traps.c:100 [inline] do_error_trap+0x10f/0x180 arch/x86/kernel/traps.c:197 do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:216 invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:1027 RIP: 0010:subflow_data_ready+0x1e6/0x290 net/mptcp/subflow.c:885 Code: 04 02 84 c0 74 06 0f 8e 91 00 00 00 41 0f b6 5e 48 31 ff 83 e3 18 89 de e8 37 ec 3d fe 84 db 0f 85 65 ff ff ff e8 fa ea 3d fe <0f> 0b e9 59 ff ff ff e8 ee ea 3d fe 48 89 ee 4c 89 ef e8 f3 77 ff RSP: 0018:ffff88811b2099b0 EFLAGS: 00010206 RAX: ffff888111197000 RBX: 0000000000000000 RCX: ffffffff82fbc609 RDX: 0000000000000100 RSI: ffffffff82fbc616 RDI: 0000000000000001 RBP: ffff8881111bc800 R08: ffff888111197000 R09: ffffed10222a82af R10: ffff888111541577 R11: ffffed10222a82ae R12: 1ffff11023641336 R13: ffff888111541000 R14: ffff88810fd4ca00 R15: ffff888111541570 tcp_child_process+0x754/0x920 net/ipv4/tcp_minisocks.c:841 tcp_v4_do_rcv+0x749/0x8b0 net/ipv4/tcp_ipv4.c:1642 tcp_v4_rcv+0x2666/0x2e60 net/ipv4/tcp_ipv4.c:1999 ip_protocol_deliver_rcu+0x29/0x1f0 net/ipv4/ip_input.c:204 ip_local_deliver_finish net/ipv4/ip_input.c:231 [inline] NF_HOOK include/linux/netfilter.h:421 [inline] ip_local_deliver+0x2da/0x390 net/ipv4/ip_input.c:252 dst_input include/net/dst.h:441 [inline] ip_rcv_finish net/ipv4/ip_input.c:428 [inline] ip_rcv_finish net/ipv4/ip_input.c:414 [inline] NF_HOOK include/linux/netfilter.h:421 [inline] ip_rcv+0xef/0x140 net/ipv4/ip_input.c:539 __netif_receive_skb_one_core+0x197/0x1e0 net/core/dev.c:5268 __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5382 process_backlog+0x1e5/0x6d0 net/core/dev.c:6226 napi_poll net/core/dev.c:6671 [inline] net_rx_action+0x3e3/0xd70 net/core/dev.c:6739 __do_softirq+0x18c/0x634 kernel/softirq.c:292 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1082 do_softirq.part.0+0x26/0x30 kernel/softirq.c:337 do_softirq arch/x86/include/asm/preempt.h:26 [inline] __local_bh_enable_ip+0x46/0x50 kernel/softirq.c:189 local_bh_enable include/linux/bottom_half.h:32 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:723 [inline] ip_finish_output2+0x78a/0x19c0 net/ipv4/ip_output.c:229 __ip_finish_output+0x471/0x720 net/ipv4/ip_output.c:306 dst_output include/net/dst.h:435 [inline] ip_local_out+0x181/0x1e0 net/ipv4/ip_output.c:125 __ip_queue_xmit+0x7a1/0x14e0 net/ipv4/ip_output.c:530 __tcp_transmit_skb+0x19dc/0x35e0 net/ipv4/tcp_output.c:1238 __tcp_send_ack.part.0+0x3c2/0x5b0 net/ipv4/tcp_output.c:3785 __tcp_send_ack net/ipv4/tcp_output.c:3791 [inline] tcp_send_ack+0x7d/0xa0 net/ipv4/tcp_output.c:3791 tcp_rcv_synsent_state_process net/ipv4/tcp_input.c:6040 [inline] tcp_rcv_state_process+0x36a4/0x49c2 net/ipv4/tcp_input.c:6209 tcp_v4_do_rcv+0x343/0x8b0 net/ipv4/tcp_ipv4.c:1651 sk_backlog_rcv include/net/sock.h:996 [inline] __release_sock+0x1ad/0x310 net/core/sock.c:2548 release_sock+0x54/0x1a0 net/core/sock.c:3064 inet_wait_for_connect net/ipv4/af_inet.c:594 [inline] __inet_stream_connect+0x57e/0xd50 net/ipv4/af_inet.c:686 inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:725 mptcp_stream_connect+0x171/0x5f0 net/mptcp/protocol.c:1920 __sys_connect_file net/socket.c:1854 [inline] __sys_connect+0x267/0x2f0 net/socket.c:1871 __do_sys_connect net/socket.c:1882 [inline] __se_sys_connect net/socket.c:1879 [inline] __x64_sys_connect+0x6f/0xb0 net/socket.c:1879 do_syscall_64+0xb7/0x3d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fb577d06469 Code: 00 f3 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 8b 0d ff 49 2b 00 f7 d8 64 89 01 48 RSP: 002b:00007fb5783d5dd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 000000000068bfa0 RCX: 00007fb577d06469 RDX: 000000000000004d RSI: 0000000020000040 RDI: 0000000000000003 RBP: 00000000ffffffff R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000041427c R14: 00007fb5783d65c0 R15: 0000000000000003 Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/39 Reported-by: Christoph Paasch Fixes: e1ff9e82e2ea ("net: mptcp: improve fallback to TCP") Suggested-by: Paolo Abeni Signed-off-by: Davide Caratti Reviewed-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/subflow.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index e1e19c76e267..9f7f3772c13c 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -873,7 +873,7 @@ static void subflow_data_ready(struct sock *sk) struct mptcp_sock *msk; msk = mptcp_sk(parent); - if (inet_sk_state_load(sk) == TCP_LISTEN) { + if ((1 << inet_sk_state_load(sk)) & (TCPF_LISTEN | TCPF_CLOSE)) { set_bit(MPTCP_DATA_READY, &msk->flags); parent->sk_data_ready(parent); return; -- 2.20.1