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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 23 Jun 2018 22:26:27 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     David Miller <davem@...emloft.net>
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()

On Sat, Jun 23, 2018 at 10:57:06AM +0900, David Miller wrote:
> From: Paul Moore <pmoore@...hat.com>
> Date: Fri, 22 Jun 2018 17:18:20 -0400
> 
> > -	const mm_segment_t old_fs = get_fs();
> > -
> > -	set_fs(KERNEL_DS);
> > -	ret_val = ipv6_renew_options(sk, opt, newtype,
> > -				     (struct ipv6_opt_hdr __user *)newopt,
> > -				     newoptlen);
> > -	set_fs(old_fs);
> 
> So is it really the case that the traditional construct:
> 
> 	set_fs(KERNEL_DS);
> 	... copy_{from,to}_user(...);
> 	set_fs(old_fs);
> 
> is no longer allowed?

s/no longer allowed/best avoided/, but IMO in this case the replacement is
too ugly to live ;-/