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mptcp: fix NULL ptr dereference in MP_JOIN error path
When token lookup on MP_JOIN 3rd ack fails, the server socket closes with a reset the incoming child. Such socket has the 'is_mptcp' flag set, but no msk socket associated - due to the failed lookup. While crafting the reset packet mptcp_established_options_mp() will try to dereference the child's master socket, causing a NULL ptr dereference. This change addresses the issue with explicit fallback to TCP in such error path. Fixes: 729cd6436f35 ("mptcp: cope better with MP_JOIN failure") Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -413,6 +413,20 @@ static void subflow_ulp_fallback(struct sock *sk,
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tcp_sk(sk)->is_mptcp = 0;
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}
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static void subflow_drop_ctx(struct sock *ssk)
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{
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struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
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if (!ctx)
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return;
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subflow_ulp_fallback(ssk, ctx);
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if (ctx->conn)
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sock_put(ctx->conn);
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kfree_rcu(ctx, rcu);
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}
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static struct sock *subflow_syn_recv_sock(const struct sock *sk,
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struct sk_buff *skb,
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struct request_sock *req,
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@ -485,10 +499,7 @@ create_child:
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if (fallback_is_fatal)
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goto dispose_child;
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if (ctx) {
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subflow_ulp_fallback(child, ctx);
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kfree_rcu(ctx, rcu);
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}
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subflow_drop_ctx(child);
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goto out;
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}
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@ -537,6 +548,7 @@ out:
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return child;
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dispose_child:
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subflow_drop_ctx(child);
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tcp_rsk(req)->drop_req = true;
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tcp_send_active_reset(child, GFP_ATOMIC);
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inet_csk_prepare_for_destroy_sock(child);
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