netdev - [PATCH net] mptcp: fix uninitialized value access

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Message-Id: <c2b96b3751ccf64357d2c6f0e7d23908dda8a601.1588157274.git.pabeni@redhat.com>
Date:   Wed, 29 Apr 2020 12:50:37 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, mptcp@...ts.01.org
Subject: [PATCH net] mptcp: fix uninitialized value access

tcp_v{4,6}_syn_recv_sock() set 'own_req' only when returning
a not NULL 'child', let's check 'own_req' only if child is
available to avoid an - unharmful - UBSAN splat.

Fixes: 20882e2cb904 ("mptcp: avoid flipping mp_capable field in syn_recv_sock()")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/mptcp/subflow.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index f412e886aa9b..2fa319a36ea5 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -522,7 +522,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	/* check for expected invariant - should never trigger, just help
 	 * catching eariler subtle bugs
 	 */
-	WARN_ON_ONCE(*own_req && child && tcp_sk(child)->is_mptcp &&
+	WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
 		     (!mptcp_subflow_ctx(child) ||
 		      !mptcp_subflow_ctx(child)->conn));
 	return child;
-- 
2.21.1