Patch "mptcp: fix locking for in-kernel listener creation" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    mptcp: fix locking for in-kernel listener creation

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-fix-locking-for-in-kernel-listener-creation.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a2c50dc9e420be8c2e8d8443cfc87b5b206db329
Author: Paolo Abeni <pabeni@xxxxxxxxxx>
Date:   Tue Feb 7 14:04:15 2023 +0100

    mptcp: fix locking for in-kernel listener creation
    
    [ Upstream commit ad2171009d968104ccda9dc517f5a3ba891515db ]
    
    For consistency, in mptcp_pm_nl_create_listen_socket(), we need to
    call the __mptcp_nmpc_socket() under the msk socket lock.
    
    Note that as a side effect, mptcp_subflow_create_socket() needs a
    'nested' lockdep annotation, as it will acquire the subflow (kernel)
    socket lock under the in-kernel listener msk socket lock.
    
    The current lack of locking is almost harmless, because the relevant
    socket is not exposed to the user space, but in future we will add
    more complexity to the mentioned helper, let's play safe.
    
    Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Reviewed-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
    Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 2b1b40199c617..3a1e8f2388665 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -891,8 +891,8 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
 {
 	int addrlen = sizeof(struct sockaddr_in);
 	struct sockaddr_storage addr;
-	struct mptcp_sock *msk;
 	struct socket *ssock;
+	struct sock *newsk;
 	int backlog = 1024;
 	int err;
 
@@ -901,13 +901,15 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
 	if (err)
 		return err;
 
-	msk = mptcp_sk(entry->lsk->sk);
-	if (!msk) {
+	newsk = entry->lsk->sk;
+	if (!newsk) {
 		err = -EINVAL;
 		goto out;
 	}
 
-	ssock = __mptcp_nmpc_socket(msk);
+	lock_sock(newsk);
+	ssock = __mptcp_nmpc_socket(mptcp_sk(newsk));
+	release_sock(newsk);
 	if (!ssock) {
 		err = -EINVAL;
 		goto out;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 15dbaa202c7cf..b0e9548f00bf1 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1570,7 +1570,7 @@ int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock)
 	if (err)
 		return err;
 
-	lock_sock(sf->sk);
+	lock_sock_nested(sf->sk, SINGLE_DEPTH_NESTING);
 
 	/* the newly created socket has to be in the same cgroup as its parent */
 	mptcp_attach_cgroup(sk, sf->sk);