From: Paolo Abeni <pabeni@xxxxxxxxxx>
[ 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@xxxxxxxxx>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/402
Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Mat Martineau <martineau@xxxxxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 {
--
2.39.2
