linux-kernel - Re: [PATCH] clean up scary strncpy(dst, src, strlen(src)) uses

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Message-Id: <20130605164804.8071867d28c1f20cad8d7d2a@linux-foundation.org>
Date:	Wed, 5 Jun 2013 16:48:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-s390@...r.kernel.org,
	devel@...verdev.osuosl.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH] clean up scary strncpy(dst, src, strlen(src)) uses

On Fri, 31 May 2013 09:18:07 -0700 Kees Cook <keescook@...omium.org> wrote:

> Fix various weird constructions of strncpy(dst, src, strlen(src)). Length
> limits should be about the space available in the destination, not
> repurposed as a method to either always include or always exclude
> a trailing NULL byte. Either the NULL should always be copied
> (using strlcpy), or it should not be copied (using something like
> memcpy). Readable code should not depend on the weird behavior of strncpy
> when it hits the length limit. Better to avoid the anti-pattern entirely.
> 
> ...
>
> --- a/Documentation/accounting/getdelays.c
> +++ b/Documentation/accounting/getdelays.c
> @@ -23,6 +23,7 @@
>  #include <sys/socket.h>
>  #include <sys/wait.h>
>  #include <signal.h>
> +#include <bsd/string.h>
>  
>  #include <linux/genetlink.h>
>  #include <linux/taskstats.h>
> @@ -299,7 +300,7 @@ int main(int argc, char *argv[])
>  			break;
>  		case 'C':
>  			containerset = 1;
> -			strncpy(containerpath, optarg, strlen(optarg) + 1);
> +			strlcpy(containerpath, optarg, sizeof(containerpath));
>  			break;
>  		case 'w':
>  			logfile = strdup(optarg);

Documentation/accounting/getdelays.c:26:24: fatal error: bsd/string.h: No such file or directory

I'll revert this part.
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