From: Qing Luo Date: Mon, 3 Aug 2026 16:16:36 +0000 (+0200) Subject: mptcp: pm: fix data race in add_addr timer callback X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=a7aad5b69d3bdaec20a3ed9284e184502450c0cd;p=thirdparty%2Fkernel%2Flinux.git mptcp: pm: fix data race in add_addr timer callback The timer callback reads entry->retrans_times outside pm.lock to decide whether to call mptcp_pm_subflow_established(). Since mptcp_pm_announced_del_timer() can concurrently set retrans_times = ADD_ADDR_RETRANS_MAX under pm.lock, a race condition exists. I discovered this issue while studying the code. AI tools helped me to verify the issue can potentially happen under race conditions. Use a local 'retransmit' flag set inside pm.lock to capture whether retransmission is still possible when the lock is taken. This allows to call mptcp_pm_subflow_established() accordingly, and not depending on the situation that can be different when checked outside the pm.lock. Fixes: 348d5c1dec60 ("mptcp: move to next addr when timeout") Cc: stable@vger.kernel.org Signed-off-by: Qing Luo Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260803-net-mptcp-misc-fixes-7-2-rc6-v2-4-b8f496d71664@kernel.org Signed-off-by: Jakub Kicinski --- diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 6afd39aea110..c71dcf887683 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -380,6 +380,7 @@ static void mptcp_pm_add_addr_timer(struct timer_list *timer) struct mptcp_sock *msk = entry->sock; struct sock *sk = (struct sock *)msk; unsigned int timeout = 0; + bool retransmit; pr_debug("msk=%p\n", msk); @@ -412,14 +413,15 @@ static void mptcp_pm_add_addr_timer(struct timer_list *timer) entry->retrans_times++; } - if (entry->retrans_times < ADD_ADDR_RETRANS_MAX) + retransmit = entry->retrans_times < ADD_ADDR_RETRANS_MAX; + if (retransmit) timeout <<= entry->retrans_times; else timeout = 0; spin_unlock_bh(&msk->pm.lock); - if (entry->retrans_times == ADD_ADDR_RETRANS_MAX) + if (!retransmit) mptcp_pm_subflow_established(msk); out: