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

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Message-ID: <20101005165159.GQ19804@ZenIV.linux.org.uk>
Date:	Tue, 5 Oct 2010 17:51:59 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@...ia.com>,
	"H. Peter Anvin" <hpa@...or.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 Tue, Oct 05, 2010 at 08:55:01AM -0700, Linus Torvalds wrote:

> 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?

Take a look at struct hash definition.  That sizeof is PATH_MAX and
do_header() will reject an entry with name longer than that.  IOW,
the whole thing is a non-issue; we can add
	if (strlen(name) >= PATH_MAX)
		BUG();
if we really care, but that's it.

As a side note, it looks like we need a fat warning about blind "improvements"
of that kind in CodingStyle; cargo-cult replacements like that can easily
hide real bugs... ;-/
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