@@ -91,7 +91,7 @@ static int __mptcp_socket_create(struct mptcp_sock *msk)
return err;
msk->first = ssock->sk;
- msk->subflow = ssock;
+ WRITE_ONCE(msk->subflow, ssock);
subflow = mptcp_subflow_ctx(ssock->sk);
list_add(&subflow->node, &msk->conn_list);
sock_hold(ssock->sk);
@@ -2309,7 +2309,7 @@ static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk)
{
if (msk->subflow) {
iput(SOCK_INODE(msk->subflow));
- msk->subflow = NULL;
+ WRITE_ONCE(msk->subflow, NULL);
}
}
@@ -3184,7 +3184,7 @@ struct sock *mptcp_sk_clone(const struct sock *sk,
msk = mptcp_sk(nsk);
msk->local_key = subflow_req->local_key;
msk->token = subflow_req->token;
- msk->subflow = NULL;
+ WRITE_ONCE(msk->subflow, NULL);
msk->in_accept_queue = 1;
WRITE_ONCE(msk->fully_established, false);
if (mp_opt->suboptions & OPTION_MPTCP_CSUMREQD)
@@ -3233,7 +3233,7 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
struct socket *listener;
struct sock *newsk;
- listener = msk->subflow;
+ listener = READ_ONCE(msk->subflow);
if (WARN_ON_ONCE(!listener)) {
*err = -EINVAL;
return NULL;
@@ -3784,10 +3784,10 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
pr_debug("msk=%p", msk);
- /* buggy applications can call accept on socket states other then LISTEN
+ /* Buggy applications can call accept on socket states other then LISTEN
* but no need to allocate the first subflow just to error out.
*/
- ssock = msk->subflow;
+ ssock = READ_ONCE(msk->subflow);
if (!ssock)
return -EINVAL;
@@ -3863,10 +3863,12 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
state = inet_sk_state_load(sk);
pr_debug("msk=%p state=%d flags=%lx", msk, state, msk->flags);
if (state == TCP_LISTEN) {
- if (WARN_ON_ONCE(!msk->subflow || !msk->subflow->sk))
+ struct socket *ssock = READ_ONCE(msk->subflow);
+
+ if (WARN_ON_ONCE(!ssock || !ssock->sk))
return 0;
- return inet_csk_listen_poll(msk->subflow->sk);
+ return inet_csk_listen_poll(ssock->sk);
}
if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
@@ -304,7 +304,11 @@ struct mptcp_sock {
struct list_head rtx_queue;
struct mptcp_data_frag *first_pending;
struct list_head join_list;
- struct socket *subflow; /* outgoing connect/listener/!mp_capable */
+ struct socket *subflow; /* outgoing connect/listener/!mp_capable
+ * The mptcp ops can safely dereference, using suitable
+ * ONCE annotation, the subflow outside the socket
+ * lock as such sock is freed after close().
+ */
struct sock *first;
struct mptcp_pm_data pm;
struct mptcp_sched_ops *sched;
The MPTCP can access the first subflow socket in a few spots outside the socket lock scope. That is actually safe, as MPTCP will delete the socket itself only after the msk sock close(). Still the such accesses causes a few KCSAN splats, as reported by Christoph. Silence the harmless warning adding a few annotation around the relevant accesses. Fixes: 71ba088ce0aa ("mptcp: cleanup accept and poll") Reported-by: Christoph Paasch <cpaasch@apple.com> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/402 Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 18 ++++++++++-------- net/mptcp/protocol.h | 6 +++++- 2 files changed, 15 insertions(+), 9 deletions(-)