linux-kernel - Re: rwx mapping between ex

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]

Date:	Thu, 1 Oct 2015 11:12:21 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Kees Cook <keescook@...omium.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	"x86@...nel.org" <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: rwx mapping between ex_table and rodata


* Thomas Gleixner <tglx@...utronix.de> wrote:

> On Mon, 28 Sep 2015, Kees Cook wrote:
> > > --- a/arch/x86/mm/init_64.c
> > > +++ b/arch/x86/mm/init_64.c
> > > @@ -1132,7 +1132,7 @@ void mark_rodata_ro(void)
> > >          * has been zapped already via cleanup_highmem().
> > >          */
> > >         all_end = roundup((unsigned long)_brk_end, PMD_SIZE);
> > > -       set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);
> > > +       set_memory_nx(text_end, (all_end - text_end) >> PAGE_SHIFT);
> > >
> > >         rodata_test();
> > >
> > >
> > 
> > That should work, yeah. I'd still like to find the default permissions and 
> > make them W+nx, though. Regardless, let's get the above added.
> 
> The default permissions are set at boot time when setting up the early page 
> tables. When we split them up later on we inherit the PTE bits and then we do 
> that _ro/nx cleanup after the overall layout has been settled.
> 
> We can't make them W+nx in the early setup without shooting ourself in the foot, 
> because we only set up at the pud/pmd level.

So I think at minimum we should do a (debug) scan in late init, of the whole 
range, for any leftover WX permissions? That would have caught this bug. (and 
might catch other existing bugs that might occur with various configs/hw-layouts.)

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/