From 1d3127542665e0a4dee20285766b147bb87402e6 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Tue, 20 Jun 2023 18:24:20 +0200 Subject: [PATCH] mptcp: fix possible list corruption on passive MPJ commit 56a666c48b038e91b76471289e2cf60c79d326b9 upstream. At passive MPJ time, if the msk socket lock is held by the user, the new subflow is appended to the msk->join_list under the msk data lock. In mptcp_release_cb()/__mptcp_flush_join_list(), the subflows in that list are moved from the join_list into the conn_list under the msk socket lock. Append and removal could race, possibly corrupting such list. Address the issue splicing the join list into a temporary one while still under the msk data lock. Found by code inspection, the race itself should be almost impossible to trigger in practice. Fixes: 3e5014909b56 ("mptcp: cleanup MPJ subflow list handling") Cc: stable@vger.kernel.org Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/mptcp/protocol.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index f481cb0..a5b330b 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -846,12 +846,12 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk, struct sock *ssk) return true; } -static void __mptcp_flush_join_list(struct sock *sk) +static void __mptcp_flush_join_list(struct sock *sk, struct list_head *join_list) { struct mptcp_subflow_context *tmp, *subflow; struct mptcp_sock *msk = mptcp_sk(sk); - list_for_each_entry_safe(subflow, tmp, &msk->join_list, node) { + list_for_each_entry_safe(subflow, tmp, join_list, node) { struct sock *ssk = mptcp_subflow_tcp_sock(subflow); bool slow = lock_sock_fast(ssk); @@ -3335,9 +3335,14 @@ static void mptcp_release_cb(struct sock *sk) for (;;) { unsigned long flags = (msk->cb_flags & MPTCP_FLAGS_PROCESS_CTX_NEED) | msk->push_pending; + struct list_head join_list; + if (!flags) break; + INIT_LIST_HEAD(&join_list); + list_splice_init(&msk->join_list, &join_list); + /* the following actions acquire the subflow socket lock * * 1) can't be invoked in atomic scope @@ -3348,8 +3353,9 @@ static void mptcp_release_cb(struct sock *sk) msk->push_pending = 0; msk->cb_flags &= ~flags; spin_unlock_bh(&sk->sk_lock.slock); + if (flags & BIT(MPTCP_FLUSH_JOIN_LIST)) - __mptcp_flush_join_list(sk); + __mptcp_flush_join_list(sk, &join_list); if (flags & BIT(MPTCP_PUSH_PENDING)) __mptcp_push_pending(sk, 0); if (flags & BIT(MPTCP_RETRANSMIT)) -- 2.7.4