linux-kernel - Re: [PATCH 1/1] initramfs: strcpy destination string overflow

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Message-ID: <4CAB4B9D.2020500@zytor.com>
Date:	Tue, 05 Oct 2010 09:00:29 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@...ia.com>,
	akpm@...ux-foundation.org, phillip@...gher.demon.co.uk,
	hsweeten@...ionengravers.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] initramfs: strcpy destination string overflow

On 10/05/2010 08:55 AM, Linus Torvalds wrote:
> On Tue, Oct 5, 2010 at 1:44 AM, Evgeny Kuznetsov
> <EXT-Eugeny.Kuznetsov@...ia.com> wrote:
>> From: Evgeny Kuznetsov <ext-eugeny.kuznetsov@...ia.com>
>>
>> Function "strcpy()" is used without check for maximum allowed
>> source string length and could cause destination string overflow.
>> "strcpy()" is replaced by "strlcpy()" to prevent destination
>> string overflow.
> 
> I think this is wrong.
> 
> If the name is too long to fit in the hash table, we should not create
> a new hash entry at all, because we'd be returning the wrong
> (truncated) name when we find it next time.
> 
> So it would be much better to just do
> 
>    if (strlen(name) >= sizeof(q->name))
>       return NULL;
> 
> in find_link(), because as far as I can tell, the hard-linking is
> always just an optimization.
> 
> Comments? Peter?

The hard-linking is unfortunately not just an optimization; if you
ignore it you will create one copy of the file and some number of
zero-length files, since the data isn't duplicated.  As such, printk'ing
an error message and ignoring it is probably the right thing to do.
Truncation is definitely wrong.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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