linux-kernel - Re: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync

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, 18 Jul 2019 11:04:57 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Joerg Roedel <jroedel@...e.de>
cc:     Joerg Roedel <joro@...tes.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/3] x86/mm: Sync also unmappings in vmalloc_sync_one()

Joerg,

On Thu, 18 Jul 2019, Joerg Roedel wrote:
> On Wed, Jul 17, 2019 at 11:43:43PM +0200, Thomas Gleixner wrote:
> > On Wed, 17 Jul 2019, Joerg Roedel wrote:
> > > +
> > > +	if (!pmd_present(*pmd_k))
> > > +		return NULL;
> > >  	else
> > >  		BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
> > 
> > So in case of unmap, this updates only the first entry in the pgd_list
> > because vmalloc_sync_all() will break out of the iteration over pgd_list
> > when NULL is returned from vmalloc_sync_one().
> > 
> > I'm surely missing something, but how is that supposed to sync _all_ page
> > tables on unmap as the changelog claims?
> 
> No, you are right, I missed that. It is a bug in this patch, the code
> that breaks out of the loop in vmalloc_sync_all() needs to be removed as
> well. Will do that in the next version.

I assume that p4d/pud do not need the pmd treatment, but a comment
explaining why would be appreciated.

Thanks,

	tglx