netdev - Re: [Patch net] smc: disallow TCP_ULP in smc

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Message-ID: <f273fcd6-05e2-68d4-56e3-31cd228fab23@linux.ibm.com>
Date:   Mon, 12 Apr 2021 08:52:05 +0200
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, Cong Wang <cong.wang@...edance.com>,
        syzbot+b54a1ce86ba4a623b7f0@...kaller.appspotmail.com,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [Patch net] smc: disallow TCP_ULP in smc_setsockopt()



On 10/04/2021 20:17, Cong Wang wrote:
> From: Cong Wang <cong.wang@...edance.com>
> 
> 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 cause is that smc_setsockopt() simply calls
> TCP setsockopt(). I do not think it makes sense to setup kTLS on
> top of SMC, so we can just disallow this.
> 
> Reported-and-tested-by: syzbot+b54a1ce86ba4a623b7f0@...kaller.appspotmail.com
> Cc: John Fastabend <john.fastabend@...il.com>
> Cc: Karsten Graul <kgraul@...ux.ibm.com>
> Signed-off-by: Cong Wang <cong.wang@...edance.com>
> ---
>  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 47340b3b514f..0d4d6d28f20c 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -2162,6 +2162,9 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
>  	struct smc_sock *smc;
>  	int val, rc;
>  
> +	if (optname == TCP_ULP)
> +		return -EOPNOTSUPP;
> +
>  	smc = smc_sk(sk);
>  
>  	/* generic setsockopts reaching us here always apply to the
> @@ -2186,7 +2189,6 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
>  	if (rc || smc->use_fallback)
>  		goto out;
>  	switch (optname) {
> -	case TCP_ULP:

Should'nt it return -EOPNOTSUPP in that case, too?

>  	case TCP_FASTOPEN:
>  	case TCP_FASTOPEN_CONNECT:
>  	case TCP_FASTOPEN_KEY:
> 

-- 
Karsten

(I'm a dude)