linux-kernel - Re: [PATCH] fs/proc/kcore.c: Omit kernel text area for hardened usercopy feature

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Message-ID: <20160906194114.GP5871@two.firstfloor.org>
Date:   Tue, 6 Sep 2016 12:41:14 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Jiri Olsa <jolsa@...hat.com>,
        Andi Kleen <andi@...stfloor.org>, Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] fs/proc/kcore.c: Omit kernel text area for hardened
 usercopy feature

On Tue, Sep 06, 2016 at 11:34:28AM -0700, Linus Torvalds wrote:
> On Tue, Sep 6, 2016 at 10:56 AM, Kees Cook <keescook@...omium.org> wrote:
> >
> > In the meantime, how about continuing to use a bounce buffer like
> > already done in the vmalloc_or_module_addr() case immediately above?
> 
> Yes please. Let's not make up even more of the user access functions
> with magical properties, for some special-case code in /proc/kcore.

I suspect it's more than just /proc/kcore, there could be also 
legitimate cases to read kernel text from /dev/mem or /dev/kmem

I suppose could add bounce buffers everywhere.

-Andi