netdev - Re: [PATCH] net/rds: using strlcpy instead of strncpy

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Message-ID: <1362453419.3768.380.camel@deadeye.wl.decadent.org.uk>
Date:	Tue, 5 Mar 2013 03:16:59 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Chen Gang <gang.chen@...anux.com>
CC:	David Laight <David.Laight@...LAB.COM>,
	<venkat.x.venkatsubra@...cle.com>,
	David Miller <davem@...emloft.net>, <rds-devel@....oracle.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net/rds: using strlcpy instead of strncpy

On Tue, 2013-03-05 at 10:32 +0800, Chen Gang wrote:
> 于 2013年03月05日 02:34, Ben Hutchings 写道:
> > On Mon, 2013-03-04 at 18:32 +0000, Ben Hutchings wrote:
> >> > On Thu, 2013-02-28 at 09:36 +0000, David Laight wrote:
> >>> > > 
> >>> > > If the target buffer ends up being copied to userspace that
> >>> > > might lead to random kernel memory being leaked.
> >> > 
> >> > Seems it is.  The last byte of 'name' is not currently initialised and
> >> > therefore is already leaked to userland.
> >> > 
> >> > But it's OK because rds_info_copy() uses memcpy() not __copy_to_user(),
> >> > so SMAP will block this leak. :-)
> > Or not, as kmap() presumably evades that.
> 
>  is this patch ok, or need improving ?

I think it is wrong, and the code should be changed to do either:

1. Zero-initialise the whole of the name, then use strlcpy().
2. Keep using strncpy(), and also set the last byte of name to 0.

> BTW:
>   excuse me, maybe my reply will be late during this week.
>   the reason:
>     my father had a serious heart disease, and is in hospital.
>     during these days, most of my time has to be in hospital.
>       (God Bless, and thank Jesus Christ, my father is safe, now).
>     within my company (Asianux), I also have something to do.

Best wishes to you both.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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