netdev - Re: [PATCH net-next] net: ipconfig: replace strncpy with strscpy

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] [day] [month] [year] [list]

Message-ID: <CAH4c4jJpfztu9mEBv_p8ACOa=h-WSTa+vJ45U0GUZ_nf0WsiRA@mail.gmail.com>
Date: Wed, 16 Apr 2025 20:31:18 +0530
From: Pranav Tyagi <pranav.tyagi03@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net, dsahern@...nel.org, 
	edumazet@...gle.com, pabeni@...hat.com, skhan@...uxfoundation.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH net-next] net: ipconfig: replace strncpy with strscpy

On Wed, Apr 16, 2025 at 4:47 PM Simon Horman <horms@...nel.org> wrote:
>
> On Tue, Apr 15, 2025 at 05:19:27PM -0700, Jakub Kicinski wrote:
> > On Tue, 15 Apr 2025 17:35:36 +0100 Simon Horman wrote:
> > > > @@ -1690,7 +1690,7 @@ static int __init ic_proto_name(char *name)
> > > >                   *v = 0;
> > > >                   if (kstrtou8(client_id, 0, dhcp_client_identifier))
> > > >                           pr_debug("DHCP: Invalid client identifier type\n");
> > > > -                 strncpy(dhcp_client_identifier + 1, v + 1, 251);
> > > > +                 strscpy(dhcp_client_identifier + 1, v + 1, 251);
> > >
> > > As an aside, I'm curious to know why the length is 251
> > > rather than 252 (sizeof(dhcp_client_identifier) -1).
> > > But that isn't strictly related to this patch.
> >
> > Isn't this because strncpy() doesn't nul-terminate, and since this is a
> > static variable if we use len - 1 we guarantee that there will be a null
> > byte at the end? If we switch to strscpy we'll make the max string len
> > 1 char shorter.
>
> Yes, that makes sense to me.
> And so I think the patch should also increase 251 to 252.

Thanks for pointing that out. I appreciate the feedback
and will send an updated version with the suggested change.
Regards