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authorPaolo Abeni <pabeni@redhat.com>2020-05-29 17:43:30 +0200
committerDavid S. Miller <davem@davemloft.net>2020-05-30 21:39:13 -0700
commit10f6d46c943d1ccd1d730d2e915226cbdeaad2d5 (patch)
tree444d6c93ad26f6ed1296e125669f744b622e3bb7 /net/mptcp
parent41be81a8d3d09acb9033799938306349328861f9 (diff)
mptcp: fix race between MP_JOIN and close
If a MP_JOIN subflow completes the 3whs while another CPU is closing the master msk, we can hit the following race: CPU1 CPU2 close() mptcp_close subflow_syn_recv_sock mptcp_token_get_sock mptcp_finish_join inet_sk_state_load mptcp_token_destroy inet_sk_state_store(TCP_CLOSE) __mptcp_flush_join_list() mptcp_sock_graft list_add_tail sk_common_release sock_orphan() <socket free> The MP_JOIN socket will be leaked. Additionally we can hit UaF for the msk 'struct socket' referenced via the 'conn' field. This change try to address the issue introducing some synchronization between the MP_JOIN 3whs and mptcp_close via the join_list spinlock. If we detect the msk is closing the MP_JOIN socket is closed, too. Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests") Signed-off-by: Paolo Abeni <pabeni@redhat.com> Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/mptcp')
-rw-r--r--net/mptcp/protocol.c42
1 files changed, 27 insertions, 15 deletions
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8959a74f707d..35bdfb4f3eae 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1266,8 +1266,12 @@ static void mptcp_close(struct sock *sk, long timeout)
mptcp_token_destroy(msk->token);
inet_sk_state_store(sk, TCP_CLOSE);
- __mptcp_flush_join_list(msk);
-
+ /* be sure to always acquire the join list lock, to sync vs
+ * mptcp_finish_join().
+ */
+ spin_lock_bh(&msk->join_list_lock);
+ list_splice_tail_init(&msk->join_list, &msk->conn_list);
+ spin_unlock_bh(&msk->join_list_lock);
list_splice_init(&msk->conn_list, &conn_list);
data_fin_tx_seq = msk->write_seq;
@@ -1623,22 +1627,30 @@ bool mptcp_finish_join(struct sock *sk)
if (!msk->pm.server_side)
return true;
- /* passive connection, attach to msk socket */
+ if (!mptcp_pm_allow_new_subflow(msk))
+ return false;
+
+ /* active connections are already on conn_list, and we can't acquire
+ * msk lock here.
+ * use the join list lock as synchronization point and double-check
+ * msk status to avoid racing with mptcp_close()
+ */
+ spin_lock_bh(&msk->join_list_lock);
+ ret = inet_sk_state_load(parent) == TCP_ESTABLISHED;
+ if (ret && !WARN_ON_ONCE(!list_empty(&subflow->node)))
+ list_add_tail(&subflow->node, &msk->join_list);
+ spin_unlock_bh(&msk->join_list_lock);
+ if (!ret)
+ return false;
+
+ /* attach to msk socket only after we are sure he will deal with us
+ * at close time
+ */
parent_sock = READ_ONCE(parent->sk_socket);
if (parent_sock && !sk->sk_socket)
mptcp_sock_graft(sk, parent_sock);
-
- ret = mptcp_pm_allow_new_subflow(msk);
- if (ret) {
- subflow->map_seq = msk->ack_seq;
-
- /* active connections are already on conn_list */
- spin_lock_bh(&msk->join_list_lock);
- if (!WARN_ON_ONCE(!list_empty(&subflow->node)))
- list_add_tail(&subflow->node, &msk->join_list);
- spin_unlock_bh(&msk->join_list_lock);
- }
- return ret;
+ subflow->map_seq = msk->ack_seq;
+ return true;
}
bool mptcp_sk_is_subflow(const struct sock *sk)