netdev - [PATCH net 1/2] mptcp: fix subflow traversal at disconnect time

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Date:   Fri,  8 Jul 2022 16:36:09 -0700
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     netdev@...r.kernel.org
Cc:     Paolo Abeni <pabeni@...hat.com>, davem@...emloft.net,
        kuba@...nel.org, edumazet@...gle.com, kishen.maloor@...el.com,
        matthieu.baerts@...sares.net, mptcp@...ts.linux.dev,
        van fantasy <g1042620637@...il.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net 1/2] mptcp: fix subflow traversal at disconnect time

From: Paolo Abeni <pabeni@...hat.com>

At disconnect time the MPTCP protocol traverse the subflows
list closing each of them. In some circumstances - MPJ subflow,
passive MPTCP socket, the latter operation can remove the
subflow from the list, invalidating the current iterator.

Address the issue using the safe list traversing helper
variant.

Reported-by: van fantasy <g1042620637@...il.com>
Fixes: b29fcfb54cd7 ("mptcp: full disconnect implementation")
Tested-by: Matthieu Baerts <matthieu.baerts@...sares.net>
Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/mptcp/protocol.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index cc21fafd9726..21a3ed64226e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2919,12 +2919,12 @@ static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
 
 static int mptcp_disconnect(struct sock *sk, int flags)
 {
-	struct mptcp_subflow_context *subflow;
+	struct mptcp_subflow_context *subflow, *tmp;
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
 	inet_sk_state_store(sk, TCP_CLOSE);
 
-	mptcp_for_each_subflow(msk, subflow) {
+	list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
 		__mptcp_close_ssk(sk, ssk, subflow, MPTCP_CF_FASTCLOSE);
-- 
2.37.0