[MPTCP] Re: [PATCH v2 9/9] don't flag parent socket as RCV_SHUTDOWN if one one subflow has closed

[Florian Westphal <fw at strlen.de>]

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Matthieu Baerts <matthieu.baerts(a)tessares.net> wrote:
> 00:07:58.688 [   14.025780] #PF: supervisor read access in kernel mode
> 00:07:58.689 [   14.026588] #PF: error_code(0x0000) - not-present page
> 00:07:58.690 [   14.027394] PGD 0 P4D 0
> 00:07:58.690 [   14.027801] Oops: 0000 [#1] SMP PTI
> 00:07:58.691 [   14.028355] CPU: 0 PID: 731 Comm: mptcp_connect Not tainted
> 5.4.0+ #5
> 00:07:58.692 [   14.029365] Hardware name: QEMU Standard PC (i440FX + PIIX,
> 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> 00:07:58.693 [   14.030752] RIP: 0010:mptcp_stream_accept+0x8d/0x160
> 00:07:58.694 [   14.031533] Code: 8b 9c 24 b0 05 00 00 49 81 c4 b0 05 00 00
> 4c 39 e3 74 71 49 8d 76 40 48 89 74 24 08 eb 08 48 8b 1b 4c 39 e3 74 5e 48
> 8b 6b 78 <48> 83 bd 78 02 00 00 00 75 ea 4c 8d bd 28 02 00 00 89 44 24 04 4c
> 00:07:58.697 [   14.034405] RSP: 0018:ffffad8d8044bdf0 EFLAGS: 00010283
> 00:07:58.698 [   14.035218] RAX: 0000000000000000 RBX: ffff96f35d0d9928 RCX:
> 0000000000000001

The faulty commit is

    make accept not allocate kernel socket struct


When doing the last version I broke tcp-ipv6 fallback.  This fixes
things:

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1512,6 +1512,15 @@ static int mptcp_listen(struct socket *sock, int backlog)
 	return err;
 }
 
+static bool is_tcp_proto(const struct proto *p)
+{
+#ifdef CONFIG_MPTCP_IPV6
+	return p == &tcp_prot || p == &tcpv6_prot;
+#else
+	return p == &tcp_prot;
+#endif
+}
+
 static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 			       int flags, bool kern)
 {
@@ -1526,7 +1535,7 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 		return -EINVAL;
 
 	err = ssock->ops->accept(sock, newsock, flags, kern);
-	if (err == 0 && newsock->sk->sk_prot != &tcp_prot) {
+	if (err == 0 && !is_tcp_proto(newsock->sk->sk_prot)) {
 		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
 		struct mptcp_subflow_context *subflow;