Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <b1177cdfc6af74a3e277bba5d9e708c4b3315ebe.1583575707.git.christophe.leroy@c-s.fr>
 <20200313033517.GA37606@ubuntu-m2-xlarge-x86>
In-Reply-To: <20200313033517.GA37606@ubuntu-m2-xlarge-x86>
From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 16 Mar 2020 15:51:32 -0700
Message-ID: <CAKwvOdm6Z+ERUcGXPbuBKmnpBUNKfL8fPOdxK2g+a1gVRWqh-Q@mail.gmail.com>
Subject: Re: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()
To:     Michael Ellerman <mpe@ellerman.id.au>
Cc:     Christophe Leroy <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hello ppc friends, did this get picked up into -next yet?

On Thu, Mar 12, 2020 at 8:35 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Sat, Mar 07, 2020 at 10:09:15AM +0000, Christophe Leroy wrote:
> > Commit 2efc7c085f05 ("powerpc/32: drop get_pteptr()"),
> > replaced get_pteptr() by virt_to_kpte(). But virt_to_kpte() lacks a
> > NULL pmd check and returns an invalid non NULL pointer when there
> > is no page table.
> >
> > Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> > Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
> > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> > ---
> >  arch/powerpc/include/asm/pgtable.h | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> > index b80bfd41828d..b1f1d5339735 100644
> > --- a/arch/powerpc/include/asm/pgtable.h
> > +++ b/arch/powerpc/include/asm/pgtable.h
> > @@ -54,7 +54,9 @@ static inline pmd_t *pmd_ptr_k(unsigned long va)
> >
> >  static inline pte_t *virt_to_kpte(unsigned long vaddr)
> >  {
> > -     return pte_offset_kernel(pmd_ptr_k(vaddr), vaddr);
> > +     pmd_t *pmd = pmd_ptr_k(vaddr);
> > +
> > +     return pmd_none(*pmd) ? NULL : pte_offset_kernel(pmd, vaddr);
> >  }
> >  #endif
> >
> > --
> > 2.25.0
> >
>
> With QEMU 4.2.0, I can confirm this fixes the panic:
>
> Tested-by: Nathan Chancellor <natechancellor@gmail.com>


-- 
Thanks,
~Nick Desaulniers