mptcp: fix lockdep false positive in mptcp_pm_nl_create_listen_socket()

commit cee4034a3db1d30c3243dd51506a9d4ab1a849fa upstream.

Christoph reports a lockdep splat in the mptcp_subflow_create_socket()
error path, when such function is invoked by
mptcp_pm_nl_create_listen_socket().

Such code path acquires two separates, nested socket lock, with the
internal lock operation lacking the "nested" annotation. Adding that
in sock_release() for mptcp's sake only could be confusing.

Instead just add a new lockclass to the in-kernel msk socket,
re-initializing the lockdep infra after the socket creation.

Fixes: ad2171009d96 ("mptcp: fix locking for in-kernel listener creation")
Cc: stable@vger.kernel.org
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/354
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Tested-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 5e38a0a..1c69e47 100644 (file)
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -987,9 +987,13 @@ out:
        return ret;
 }
 
+static struct lock_class_key mptcp_slock_keys[2];
+static struct lock_class_key mptcp_keys[2];
+
 static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
                                            struct mptcp_pm_addr_entry *entry)
 {
+       bool is_ipv6 = sk->sk_family == AF_INET6;
        int addrlen = sizeof(struct sockaddr_in);
        struct sockaddr_storage addr;
        struct socket *ssock;
@@ -1006,6 +1010,18 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
        if (!newsk)
                return -EINVAL;
 
+       /* The subflow socket lock is acquired in a nested to the msk one
+        * in several places, even by the TCP stack, and this msk is a kernel
+        * socket: lockdep complains. Instead of propagating the _nested
+        * modifiers in several places, re-init the lock class for the msk
+        * socket to an mptcp specific one.
+        */
+       sock_lock_init_class_and_name(newsk,
+                                     is_ipv6 ? "mlock-AF_INET6" : "mlock-AF_INET",
+                                     &mptcp_slock_keys[is_ipv6],
+                                     is_ipv6 ? "msk_lock-AF_INET6" : "msk_lock-AF_INET",
+                                     &mptcp_keys[is_ipv6]);
+
        lock_sock(newsk);
        ssock = __mptcp_nmpc_socket(mptcp_sk(newsk));
        release_sock(newsk);