linux-kernel - Re: [PATCH 4.4 1/2] x86/vdso: Remove direct HPET mapping into userspace

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Date:   Sun, 27 Oct 2019 14:50:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 4.4 1/2] x86/vdso: Remove direct HPET mapping into
 userspace

On Wed, Oct 23, 2019 at 04:05:47PM +0300, Konstantin Khlebnikov wrote:
> On 23/10/2019 15.07, Konstantin Khlebnikov wrote:
> > commit 1ed95e52d902035e39a715ff3a314a893a96e5b7 upstream.
> > 
> > Commit d96d87834d5b870402a4a5b565706a4869ebc020 in v4.4.190 which is
> > backport of upstream commit 1ed95e52d902035e39a715ff3a314a893a96e5b7
> > removed only HPET access from vdso but leaved HPET mapped in "vvar".
> > So userspace still could read HPET directly and confuse hardware.
> > 
> > This patch removes mapping HPET page into userspace.
> > 
> > Fixes: d96d87834d5b ("x86/vdso: Remove direct HPET access through the vDSO") # v4.4.190
> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> > Link: https://lore.kernel.org/lkml/6fd42b2b-e29a-1fd6-03d1-e9da9192e6c5@yandex-team.ru/
> > ---
> >   arch/x86/entry/vdso/vma.c |   14 --------------
> >   1 file changed, 14 deletions(-)
> > 
> > diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> > index 6b46648588d8..cc0a3c16a95d 100644
> > --- a/arch/x86/entry/vdso/vma.c
> > +++ b/arch/x86/entry/vdso/vma.c
> > @@ -18,7 +18,6 @@
> >   #include <asm/vdso.h>
> >   #include <asm/vvar.h>
> >   #include <asm/page.h>
> > -#include <asm/hpet.h>
> >   #include <asm/desc.h>
> >   #include <asm/cpufeature.h>
> > @@ -159,19 +158,6 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
> >   	if (ret)
> >   		goto up_fail;
> > -#ifdef CONFIG_HPET_TIMER
> > -	if (hpet_address && image->sym_hpet_page) {
> 
> Probably this patch is not required.
> It seems after removing symbol "hpet_page" from vdso code
> image->sym_hpet_page always is NULL and this branch never executed.

Ok, so these two patches are not needed?  I'll drop them from my
todo-queue, thanks.

greg k-h