linux-kernel - Re: [PATCH] af_iucv: Move sockaddr length checks to before accessing sa

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Message-Id: <20170613.161542.837461878998748762.davem@davemloft.net>
Date:   Tue, 13 Jun 2017 16:15:42 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     mjurczyk@...gle.com
Cc:     jwi@...ux.vnet.ibm.com, ubraun@...ux.vnet.ibm.com,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] af_iucv: Move sockaddr length checks to before
 accessing sa_family in bind and connect handlers

From: Mateusz Jurczyk <mjurczyk@...gle.com>
Date: Tue, 13 Jun 2017 19:42:28 +0200

> 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.
> 
> Signed-off-by: Mateusz Jurczyk <mjurczyk@...gle.com>
...
>  	/* Verify the input sockaddr */
> -	if (!addr || addr->sa_family != AF_IUCV)
> -		return -EINVAL;
> -
> -	if (addr_len < sizeof(struct sockaddr_iucv))
> +	if (!addr || addr_len < sizeof(struct sockaddr_iucv) ||
> +	    addr->sa_family != AF_IUCV)

The 'addr' can never be NULL so please remove that check, thank you.