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

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Date:   Tue, 15 Aug 2017 18:51:32 +0200
From:   Phil Sutter <phil@....cc>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: [iproute PATCH 50/51] Check user supplied interface name lengths

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.

Thanks, Phil