From: Paolo Abeni pabeni@redhat.com
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 --- net/mptcp/pm_netlink.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 56628b52d100..5c8dea49626c 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -997,9 +997,13 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet, 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; @@ -1016,6 +1020,18 @@ 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);