mptcp: stop using the mptcp_has_another_subflow() helper

The mentioned helper requires the msk socket lock, and the current callers don't own it nor can't acquire it, so the access is racy. All the current callers are really checking for infinite mapping fallback, and the latter condition is explicitly tracked by the relevant msk variable: we can safely remove the caller usage - and the caller itself. The issue is present since MP_FAIL implementation, but the fix only applies since the infinite fallback support, ence the somewhat unexpected fixes tag. Fixes: 0530020 ("mptcp: track and update contiguous data status") Acked-and-tested-by: Geliang Tang <[email protected]> Signed-off-by: Paolo Abeni <[email protected]> Signed-off-by: Mat Martineau <[email protected]> Signed-off-by: Jakub Kicinski <[email protected]>
niw · May 20, 2022 · 7b16871 · 7b16871
1 parent 9ad084d
commit 7b16871
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Showing 3 changed files with 2 additions and 16 deletions.
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
@@ -303,7 +303,7 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq)
 
 	pr_debug("fail_seq=%llu", fail_seq);
 
-	if (mptcp_has_another_subflow(sk) || !READ_ONCE(msk->allow_infinite_fallback))
+	if (!READ_ONCE(msk->allow_infinite_fallback))
 		return;
 
 	if (!READ_ONCE(subflow->mp_fail_response_expect)) {

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
@@ -650,19 +650,6 @@ static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
 	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
 }
 
-static inline bool mptcp_has_another_subflow(struct sock *ssk)
-{
-	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk), *tmp;
-	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
-
-	mptcp_for_each_subflow(msk, tmp) {
-		if (tmp != subflow)
-			return true;
-	}
-
-	return false;
-}
-
 void __init mptcp_proto_init(void);
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 int __init mptcp_proto_v6_init(void);

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
@@ -1233,8 +1233,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
 	if (!__mptcp_check_fallback(msk)) {
 		/* RFC 8684 section 3.7. */
 		if (subflow->send_mp_fail) {
-			if (mptcp_has_another_subflow(ssk) ||
-			    !READ_ONCE(msk->allow_infinite_fallback)) {
+			if (!READ_ONCE(msk->allow_infinite_fallback)) {
 				ssk->sk_err = EBADMSG;
 				tcp_set_state(ssk, TCP_CLOSE);
 				subflow->reset_transient = 0;