linux-kernel - Re: [PATCH] IPVS: replace sprintf to snprintf to avoid stack buffer overflow

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Date:	Wed, 07 Apr 2010 18:09:54 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Simon Horman <horms@...ge.net.au>
CC:	wzt.wzt@...il.com, linux-kernel@...r.kernel.org,
	Wensong Zhang <wensong@...ux-vs.org>,
	Julian Anastasov <ja@....bg>, netdev@...r.kernel.org,
	lvs-devel@...r.kernel.org
Subject: Re: [PATCH] IPVS: replace sprintf to snprintf to avoid stack buffer
 overflow

Simon Horman wrote:
> On Tue, Apr 06, 2010 at 10:50:20AM +0800, wzt.wzt@...il.com wrote:
>> IPVS not check the length of pp->name, use sprintf will cause stack buffer overflow.
>> struct ip_vs_protocol{} declare name as char *, if register a protocol as:
>> struct ip_vs_protocol ip_vs_test = {
>>         .name =			"aaaaaaaa....128...aaa",
>> 	.debug_packet =         ip_vs_tcpudp_debug_packet,
>> };
>>
>> when called ip_vs_tcpudp_debug_packet(), sprintf(buf, "%s TRUNCATED", pp->name); 
>> will cause stack buffer overflow.
>>
>> Signed-off-by: Zhitong Wang <zhitong.wangzt@...baba-inc.com>
> 
> I think that the simple answer is, don't do that.

Indeed.

> But your patch seems entirely reasonable to me.
> 
> Acked-by: Simon Horman <horms@...ge.net.au>
> 
> Patrick, please consider merging this.

I think this fix is a bit silly, we can simply print the name in
the pr_debug() statement and avoid both the potential overflow
and truncation.

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