From: Paolo Abeni pabeni@redhat.com
[ Upstream commit 5b825727d0871b23e8867f6371183e61628b4a26 ]
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 Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Mat Martineau martineau@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/mptcp/protocol.c | 18 ++++++++++-------- net/mptcp/protocol.h | 6 +++++- 2 files changed, 15 insertions(+), 9 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 676a6d24b4b71..f5c0a56f0f0ca 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -103,7 +103,7 @@ 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); @@ -2254,7 +2254,7 @@ 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); } }
@@ -3109,7 +3109,7 @@ 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) @@ -3157,7 +3157,7 @@ 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; @@ -3723,10 +3723,10 @@ 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;
@@ -3800,10 +3800,12 @@ 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) { diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index d6469b6ab38e3..84427b3697d89 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -306,7 +306,11 @@ 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 {