From: Paolo Abeni pabeni@redhat.com
commit def5b7b2643ebba696fc60ddf675dca13f073486 upstream.
We have races similar to the one addressed by the previous patch between subflow failing and additional subflow creation. They are just harder to trigger.
The solution is similar. Use a separate flag to track the condition 'socket state prevent any additional subflow creation' protected by the fallback lock.
The socket fallback makes such flag true, and also receiving or sending an MP_FAIL option.
The field 'allow_infinite_fallback' is now always touched under the relevant lock, we can drop the ONCE annotation on write.
Fixes: 478d770008b0 ("mptcp: send out MP_FAIL when data checksum fails") Cc: stable@vger.kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Matthieu Baerts (NGI0) matttbe@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Link: https://patch.msgid.link/20250714-net-mptcp-fallback-races-v1-2-391aff963322... Signed-off-by: Jakub Kicinski kuba@kernel.org [ Conflicts in subflow.c, because commit f1f26512a9bf ("mptcp: use plain bool instead of custom binary enum") and commit 46a5d3abedbe ("mptcp: fix typos in comments") are not in this version. Both are causing conflicts in the context, and the same modifications can still be applied. Same in protocol.h with commit b8dc6d6ce931 ("mptcp: fix rcv buffer auto-tuning"). Conflicts in protocol.c because commit ee2708aedad0 ("mptcp: use get_retrans wrapper") is not in this version and refactor the code in __mptcp_retrans(), but the modification can still be applied, just not at the same indentation level. ] Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org --- net/mptcp/pm.c | 8 +++++++- net/mptcp/protocol.c | 11 ++++++----- net/mptcp/protocol.h | 7 +++++-- net/mptcp/subflow.c | 19 ++++++++++++++----- 4 files changed, 32 insertions(+), 13 deletions(-)
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 34120694ad49..6392973b1fa7 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -309,8 +309,14 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq)
pr_debug("fail_seq=%llu\n", fail_seq);
- if (!READ_ONCE(msk->allow_infinite_fallback)) + /* After accepting the fail, we can't create any other subflows */ + spin_lock_bh(&msk->fallback_lock); + if (!msk->allow_infinite_fallback) { + spin_unlock_bh(&msk->fallback_lock); return; + } + msk->allow_subflows = false; + spin_unlock_bh(&msk->fallback_lock);
if (!subflow->fail_tout) { pr_debug("send MP_FAIL response and infinite map\n"); diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 904a348daa51..73e298f276a8 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -885,7 +885,7 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk) static void mptcp_subflow_joined(struct mptcp_sock *msk, struct sock *ssk) { mptcp_subflow_ctx(ssk)->map_seq = READ_ONCE(msk->ack_seq); - WRITE_ONCE(msk->allow_infinite_fallback, false); + msk->allow_infinite_fallback = false; mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC); }
@@ -897,7 +897,7 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk) return false;
spin_lock_bh(&msk->fallback_lock); - if (__mptcp_check_fallback(msk)) { + if (!msk->allow_subflows) { spin_unlock_bh(&msk->fallback_lock); return false; } @@ -2707,7 +2707,7 @@ static void __mptcp_retrans(struct sock *sk) dfrag->already_sent = max(dfrag->already_sent, info.sent); tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle, info.size_goal); - WRITE_ONCE(msk->allow_infinite_fallback, false); + msk->allow_infinite_fallback = false; } spin_unlock_bh(&msk->fallback_lock);
@@ -2835,7 +2835,8 @@ static int __mptcp_init_sock(struct sock *sk) WRITE_ONCE(msk->first, NULL); inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss; WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk))); - WRITE_ONCE(msk->allow_infinite_fallback, true); + msk->allow_infinite_fallback = true; + msk->allow_subflows = true; msk->recovery = false;
mptcp_pm_data_init(msk); @@ -3673,7 +3674,7 @@ bool mptcp_finish_join(struct sock *ssk) /* active subflow, already present inside the conn_list */ if (!list_empty(&subflow->node)) { spin_lock_bh(&msk->fallback_lock); - if (__mptcp_check_fallback(msk)) { + if (!msk->allow_subflows) { spin_unlock_bh(&msk->fallback_lock); return false; } diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index a3acc7042ee9..e1637443203e 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -314,12 +314,14 @@ struct mptcp_sock { u64 time; /* start time of measurement window */ u64 rtt_us; /* last maximum rtt of subflows */ } rcvq_space; + bool allow_subflows;
u32 setsockopt_seq; char ca_name[TCP_CA_NAME_MAX];
- spinlock_t fallback_lock; /* protects fallback and - * allow_infinite_fallback + spinlock_t fallback_lock; /* protects fallback, + * allow_infinite_fallback and + * allow_join */ };
@@ -991,6 +993,7 @@ static inline bool __mptcp_try_fallback(struct mptcp_sock *msk) return false; }
+ msk->allow_subflows = false; set_bit(MPTCP_FALLBACK_DONE, &msk->flags); spin_unlock_bh(&msk->fallback_lock); return true; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index d21109a130ec..cff232810692 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1168,20 +1168,29 @@ static void subflow_sched_work_if_closed(struct mptcp_sock *msk, struct sock *ss mptcp_schedule_work(sk); }
-static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) +static bool mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk); unsigned long fail_tout;
+ /* we are really failing, prevent any later subflow join */ + spin_lock_bh(&msk->fallback_lock); + if (!msk->allow_infinite_fallback) { + spin_unlock_bh(&msk->fallback_lock); + return false; + } + msk->allow_subflows = false; + spin_unlock_bh(&msk->fallback_lock); + /* greceful failure can happen only on the MPC subflow */ if (WARN_ON_ONCE(ssk != READ_ONCE(msk->first))) - return; + return false;
/* since the close timeout take precedence on the fail one, * no need to start the latter when the first is already set */ if (sock_flag((struct sock *)msk, SOCK_DEAD)) - return; + return true;
/* we don't need extreme accuracy here, use a zero fail_tout as special * value meaning no fail timeout at all; @@ -1193,6 +1202,7 @@ static void mptcp_subflow_fail(struct mptcp_sock *msk, struct sock *ssk) tcp_send_ack(ssk);
mptcp_reset_tout_timer(msk, subflow->fail_tout); + return true; }
static bool subflow_check_data_avail(struct sock *ssk) @@ -1261,12 +1271,11 @@ static bool subflow_check_data_avail(struct sock *ssk) (subflow->mp_join || subflow->valid_csum_seen)) { subflow->send_mp_fail = 1;
- if (!READ_ONCE(msk->allow_infinite_fallback)) { + if (!mptcp_subflow_fail(msk, ssk)) { subflow->reset_transient = 0; subflow->reset_reason = MPTCP_RST_EMIDDLEBOX; goto reset; } - mptcp_subflow_fail(msk, ssk); WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_DATA_AVAIL); return true; }