netdev - Re: [PATCH] net/rds: using strlcpy instead of strncpy

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Message-ID: <1362454672.3768.383.camel@deadeye.wl.decadent.org.uk>
Date:	Tue, 5 Mar 2013 03:37:52 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Chen Gang <gang.chen@...anux.com>
CC:	David Laight <David.Laight@...LAB.COM>,
	<venkat.x.venkatsubra@...cle.com>,
	David Miller <davem@...emloft.net>, <rds-devel@....oracle.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net/rds: using strlcpy instead of strncpy

On Tue, 2013-03-05 at 11:32 +0800, Chen Gang wrote:
> 于 2013年03月05日 11:16, Ben Hutchings 写道:
> > I think it is wrong, and the code should be changed to do either:
> > 
> > 1. Zero-initialise the whole of the name, then use strlcpy().
> > 2. Keep using strncpy(), and also set the last byte of name to 0.
> > 
> 
>   I think what I have done is just like your choice "2."
>   for me, I think they are equal:
> 
> -		strncpy(ctr.name, names[i], sizeof(ctr.name) - 1);
> +		strlcpy(ctr.name, names[i], sizeof(ctr.name));
> 
> 
> 		strncpy(ctr.name, names[i], sizeof(ctr.name) - 1);
> + 		ctr.name[sizeof(ctr.name) - 1] = '\0';

They are not.  strncpy() pads with zeroes to the end of the given buffer
whereas strlcpy() adds only a single zero byte (and truncates if
necessary to fit the zero byte).

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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