From 42c231e119e1b335895ec6cc52c120b1e5a31648 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 12 Feb 2021 20:40:28 +0000 Subject: [PATCH] mptcp: dispose initial struct socket when its subflow is closed Christoph Paasch reported following crash: dst_release underflow WARNING: CPU: 0 PID: 1319 at net/core/dst.c:175 dst_release+0xc1/0xd0 net/core/dst.c:175 CPU: 0 PID: 1319 Comm: syz-executor217 Not tainted 5.11.0-rc6af8e85128b4d0d24083c5cac646e891227052e0c #70 Call Trace: rt_cache_route+0x12e/0x140 net/ipv4/route.c:1503 rt_set_nexthop.constprop.0+0x1fc/0x590 net/ipv4/route.c:1612 __mkroute_output net/ipv4/route.c:2484 [inline] ... The worker leaves msk->subflow alone even when it happened to close the subflow ssk associated with it. Fixes: 866f26f2a9c33b ("mptcp: always graft subflow socket to parent") Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/157 Reported-by: Christoph Paasch Suggested-by: Paolo Abeni Acked-by: Paolo Abeni Signed-off-by: Florian Westphal --- net/mptcp/protocol.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 471735b2c5c09..cb33137c07cf1 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2106,6 +2106,14 @@ static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk) return backup; } +static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk) +{ + if (msk->subflow) { + iput(SOCK_INODE(msk->subflow)); + msk->subflow = NULL; + } +} + /* subflow sockets can be either outgoing (connect) or incoming * (accept). * @@ -2150,6 +2158,9 @@ void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, if (ssk == msk->last_snd) msk->last_snd = NULL; + + if (msk->subflow && ssk == msk->subflow->sk) + mptcp_dispose_initial_subflow(msk); } static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu) @@ -2538,12 +2549,6 @@ static void __mptcp_destroy_sock(struct sock *sk) might_sleep(); - /* dispose the ancillatory tcp socket, if any */ - if (msk->subflow) { - iput(SOCK_INODE(msk->subflow)); - msk->subflow = NULL; - } - /* be sure to always acquire the join list lock, to sync vs * mptcp_finish_join(). */ @@ -2568,6 +2573,7 @@ static void __mptcp_destroy_sock(struct sock *sk) sk_stream_kill_queues(sk); xfrm_sk_free_policy(sk); sk_refcnt_debug_release(sk); + mptcp_dispose_initial_subflow(msk); sock_put(sk); }