linux-kernel - Re: [patch 3/7] add kstrndup

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Date:	Fri, 11 May 2007 14:18:18 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	René Scharfe <rene.scharfe@...fire.ath.cx>
CC:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>,
	Akinobu Mita <akinobu.mita@...il.com>,
	Arnaldo Carvalho de Melo <acme@...driva.com>,
	Al Viro <viro@....linux.org.uk>,
	Panagiotis Issaris <takis@...aris.org>
Subject: Re: [patch 3/7] add kstrndup

René Scharfe wrote:
>> +	len = strlen(s);
>> +	if (len > max)
>> +		len = max;
>>     
>
> You can avoid to run beyond max and save two lines by using strnlen:
>
> 	len = strnlen(s, max);
>   

OK.  Didn't know about strnlen.

Subject: Use strnlen in kstrndup

strnlen prevents over-reading the input.

Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>
Cc: René Scharfe <rene.scharfe@...fire.ath.cx>

---
 mm/util.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

===================================================================
--- a/mm/util.c
+++ b/mm/util.c
@@ -53,9 +53,7 @@ char *kstrndup(const char *s, size_t max
 	if (!s)
 		return NULL;
 
-	len = strlen(s);
-	if (len > max)
-		len = max;
+	len = strnlen(s, max);
 	buf = kmalloc_track_caller(len+1, gfp);
  	if (buf) {
 		memcpy(buf, s, len);


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