netdev - Re: [PATCH net-next 2/2] af_iucv: Move sockaddr length checks to before accessing sa

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Message-ID: <90c818a5-af59-3115-64c2-582c2dcc520b@hartkopp.net>
Date:   Fri, 23 Jun 2017 19:36:12 +0200
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Julian Wiedmann <jwi@...ux.vnet.ibm.com>,
        David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Stefan Raspl <raspl@...ux.vnet.ibm.com>,
        Ursula Braun <ubraun@...ux.vnet.ibm.com>
Subject: Re: [PATCH net-next 2/2] af_iucv: Move sockaddr length checks to
 before accessing sa_family in bind and connect handlers



On 06/23/2017 07:32 PM, Julian Wiedmann wrote:
> From: Mateusz Jurczyk <mjurczyk@...gle.com>
> 
> Verify that the caller-provided sockaddr structure is large enough to
> contain the sa_family field, before accessing it in bind() and connect()
> handlers of the AF_IUCV socket. Since neither syscall enforces a minimum
> size of the corresponding memory region, very short sockaddrs (zero or
> one byte long) result in operating on uninitialized memory while
> referencing .sa_family.

Won't it make sense to generally check the minimum length for .sa_family at a
single point before fixing all called sites?

Regards,
Oliver

> 
> Fixes: 52a82e23b9f2 ("af_iucv: Validate socket address length in iucv_sock_bind()")
> Signed-off-by: Mateusz Jurczyk <mjurczyk@...gle.com>
> [jwi: removed unneeded null-check for addr]
> Signed-off-by: Julian Wiedmann <jwi@...ux.vnet.ibm.com>
> ---
>  net/iucv/af_iucv.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
> index 05112094d76b..ac033e413bc5 100644
> --- a/net/iucv/af_iucv.c
> +++ b/net/iucv/af_iucv.c
> @@ -715,10 +715,8 @@ static int iucv_sock_bind(struct socket *sock, struct sockaddr *addr,
>  	char uid[9];
>  
>  	/* Verify the input sockaddr */
> -	if (!addr || addr->sa_family != AF_IUCV)
> -		return -EINVAL;
> -
> -	if (addr_len < sizeof(struct sockaddr_iucv))
> +	if (addr_len < sizeof(struct sockaddr_iucv) ||
> +	    addr->sa_family != AF_IUCV)
>  		return -EINVAL;
>  
>  	lock_sock(sk);
> @@ -862,7 +860,7 @@ static int iucv_sock_connect(struct socket *sock, struct sockaddr *addr,
>  	struct iucv_sock *iucv = iucv_sk(sk);
>  	int err;
>  
> -	if (addr->sa_family != AF_IUCV || alen < sizeof(struct sockaddr_iucv))
> +	if (alen < sizeof(struct sockaddr_iucv) || addr->sa_family != AF_IUCV)
>  		return -EINVAL;
>  
>  	if (sk->sk_state != IUCV_OPEN && sk->sk_state != IUCV_BOUND)
>