netdev - Re: [PATCH] ipv6: avoid copy_from_user() via ipv6_renew_options

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Date:   Sun, 24 Jun 2018 16:48:37 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     viro@...IV.linux.org.uk
Cc:     pmoore@...hat.com, netdev@...r.kernel.org, selinux@...ho.nsa.gov,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH] ipv6: avoid copy_from_user() via
 ipv6_renew_options_kern()

From: Al Viro <viro@...IV.linux.org.uk>
Date: Sat, 23 Jun 2018 23:21:07 +0100

> BTW, I wonder if the life would be simpler with do_ipv6_setsockopt() doing
> the copy-in and verifying ipv6_optlen(*hdr) <= newoptlen; that would've
> simplified ipv6_renew_option{,s}() quite a bit and completely eliminated
> ipv6_renew_options_kern()...

I agree that this makes things a lot simpler.

One thing that drives me crazy though is this inherit stuff:

> +	ipv6_renew_option(newtype == IPV6_HOPOPTS ? newopt :
> +				opt ? opt->hopopt : NULL,

Why don't we pass the type into ipv6_renew_option() and have it
do this pointer dance instead?

That's going to definitely be easier to read.

I don't know enough about this code to give feedback about the
option length handling wrt. copies, sorry.