netdev - Re: [iproute PATCH 50/51] Check user supplied interface name lengths

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Date:   Fri, 1 Sep 2017 18:56:29 +0200
From:   Phil Sutter <phil@....cc>
To:     Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org
Subject: Re: [iproute PATCH 50/51] Check user supplied interface name lengths

Hi Stephen,

On Tue, Aug 15, 2017 at 06:51:32PM +0200, Phil Sutter wrote:
> On Tue, Aug 15, 2017 at 09:09:45AM -0700, Stephen Hemminger wrote:
> > On Sat, 12 Aug 2017 14:05:09 +0200
> > Phil Sutter <phil@....cc> wrote:
> > 
> > > +void assert_valid_dev_name(const char *, const char *);
> > 
> > Not a fan of long function names.
> > “I have only made this letter longer because I have not had the time to make it shorter."
> 
> :)
> 
> > Maybe just add a new function addattr_ifname() and add the checking there?
> 
> It is not only about netlink attributes - these are in fact
> unproblematic, since they allow for interface names longer than
> IFNAMSIZ-1 and the kernel will then reject. The length check has to
> happen before copying into any IFNAMSIZ-sized buffer takes place (e.g.
> ifr_name of struct ifreq). Logically I would prefer to perform the
> checks right at the point user input parsing takes place since it
> belongs there.
> 
> I could rename the function to 'ifname_valid' instead? I liked having
> 'assert' in the name though, since the function calls exit() on error.

Any thoughts on this?

Cheers, Phil