linux-kernel - Re: + lib-stringc-strlcpy-might-read-too-far.patch added to -mm tree

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Message-ID: <20140415111800.GW4963@mwanda>
Date:	Tue, 15 Apr 2014 14:18:00 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: + lib-stringc-strlcpy-might-read-too-far.patch added to -mm tree

On Tue, Apr 15, 2014 at 01:49:38PM +0300, Alexey Dobriyan wrote:
> Return value matters. It may not matter for kernel, because kernel is
> not heavy string user.
> But it is better to not diverge from master code:
> http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/string/strlcpy.c?rev=1.11
> 

Oh...  Hm.  Maybe we should drop this patch then.

> Counter-rationale:
> * strlcpy() accepts strings, so if you're giving raw buffer you're
> doing it wrong.
> * last byte of last page argument is bogus because kernel copies data
> from userspace first.

The last byte of the page argument seems possible:

	foo = kmalloc();
	copy_from_user(foo, arg, sizeof(foo));
	strlcpy(dest.str, foo->bar, sizeof(dest.str));

It's a very unlikely scenario.  You have to be very unlucky to hit it at
all.

regards,
dan carpenter
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