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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160902161530.GB31273@krava>
Date:   Fri, 2 Sep 2016 18:15:30 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] fs/proc/kcore.c: Omit kernel text area for hardened
 usercopy feature

On Fri, Sep 02, 2016 at 08:17:13AM -0700, Andi Kleen wrote:
> On Fri, Sep 02, 2016 at 02:25:45PM +0200, Jiri Olsa wrote:
> > One of the bullets for hardened usercopy feature is:
> >   - object must not overlap with kernel text
> > 
> > which is what we expose via /proc/kcore. We can hit
> > this check and crash the system very easily just by
> > reading the text area in kcore file:
> > 
> >   usercopy: kernel memory exposure attempt detected from ffffffff8179a01f (<kernel text>) (4065 bytes)
> >   kernel BUG at mm/usercopy.c:75!
> > 
> > Omitting kernel text area from kcore when there's
> > hardened usercopy feature is enabled.
> 
> That will completely break PT decoding, which relies on looking
> at the kernel text in /proc/kcore.
> 
> Need a different fix here, perhaps some special copy function
> that is not hardened.

ok, I'll try to come up with something

thanks,
jirka