From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [RFC PATCH v2] ipv6: make ipv6_renew_options()
 interrupt/kernel safe
Date: Wed, 04 Jul 2018 14:28:53 +0900 (KST)
Message-ID: <20180704.142853.1524154785411171806.davem@davemloft.net>
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To: pmoore@redhat.com
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From: Paul Moore <pmoore@redhat.com>
Date: Mon, 02 Jul 2018 14:20:52 -0400

> -static int ipv6_renew_option(void *ohdr,
> -			     struct ipv6_opt_hdr __user *newopt, int newoptlen,
> -			     int inherit,
> -			     struct ipv6_opt_hdr **hdr,
> -			     char **p)
> +static void ipv6_renew_option(int renewtype,
> +			      struct ipv6_opt_hdr **dest,
> +			      struct ipv6_opt_hdr *old,
> +			      struct ipv6_opt_hdr *new,
> +			      int newtype, char **p)
>  {
 ...
> +	p += CMSG_ALIGN(ipv6_optlen(*dest));

I don't think this actually advances the pointer in the caller,
you need something like:

	*p += CMSG_ALIGN(ipv6_optlen(*dest));