linux-kernel - [PATCH 5.4 085/141] smc: disallow TCP_ULP in smc

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Message-Id: <20210517140245.647272111@linuxfoundation.org>
Date:   Mon, 17 May 2021 16:02:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, John Fastabend <john.fastabend@...il.com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        Cong Wang <cong.wang@...edance.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>,
        syzbot+b54a1ce86ba4a623b7f0@...kaller.appspotmail.com
Subject: [PATCH 5.4 085/141] smc: disallow TCP_ULP in smc_setsockopt()

From: Cong Wang <cong.wang@...edance.com>

[ Upstream commit 8621436671f3a4bba5db57482e1ee604708bf1eb ]

syzbot is able to setup kTLS on an SMC socket which coincidentally
uses sk_user_data too. Later, kTLS treats it as psock so triggers a
refcnt warning. The root cause is that smc_setsockopt() simply calls
TCP setsockopt() which includes TCP_ULP. I do not think it makes
sense to setup kTLS on top of SMC sockets, so we should just disallow
this setup.

It is hard to find a commit to blame, but we can apply this patch
since the beginning of TCP_ULP.

Reported-and-tested-by: syzbot+b54a1ce86ba4a623b7f0@...kaller.appspotmail.com
Fixes: 734942cc4ea6 ("tcp: ULP infrastructure")
Cc: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/smc/af_smc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index dc09a72f8110..51986f7ead81 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1709,6 +1709,9 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
 	struct smc_sock *smc;
 	int val, rc;
 
+	if (level == SOL_TCP && optname == TCP_ULP)
+		return -EOPNOTSUPP;
+
 	smc = smc_sk(sk);
 
 	/* generic setsockopts reaching us here always apply to the
@@ -1730,7 +1733,6 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
 	if (rc || smc->use_fallback)
 		goto out;
 	switch (optname) {
-	case TCP_ULP:
 	case TCP_FASTOPEN:
 	case TCP_FASTOPEN_CONNECT:
 	case TCP_FASTOPEN_KEY:
-- 
2.30.2