2020-03-07 10:10:32

by Christophe Leroy

Subject: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()

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 <[email protected]>
Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
Signed-off-by: Christophe Leroy <[email protected]>
---
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

2020-03-13 03:37:17

by Nathan Chancellor

Subject: Re: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()

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 <[email protected]>
> Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> 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 <[email protected]>

2020-03-16 22:52:58

by Nick Desaulniers

Subject: Re: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()

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

On Thu, Mar 12, 2020 at 8:35 PM Nathan Chancellor
<[email protected]> 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 <[email protected]>
> > Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
> > Signed-off-by: Christophe Leroy <[email protected]>
> > ---
> > 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 <[email protected]>



--
Thanks,
~Nick Desaulniers

2020-03-16 23:52:47

by Michael Ellerman

Subject: Re: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()

Nick Desaulniers <[email protected]> writes:
> Hello ppc friends, did this get picked up into -next yet?

Not yet.

It's in my next-test, but it got stuck there because some subsequent
patches caused some CI errors that I had to debug.

I'll push it to next today.

cheers

> On Thu, Mar 12, 2020 at 8:35 PM Nathan Chancellor
> <[email protected]> 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 <[email protected]>
>> > Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
>> > Signed-off-by: Christophe Leroy <[email protected]>
>> > ---
>> > 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 <[email protected]>
>
>
>
> --
> Thanks,
> ~Nick Desaulniers

2020-03-17 13:16:19

by Michael Ellerman

Subject: Re: [PATCH] powerpc/32: Fix missing NULL pmd check in virt_to_kpte()

On Sat, 2020-03-07 at 10:09:15 UTC, 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 <[email protected]>
> Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
> Signed-off-by: Christophe Leroy <[email protected]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/cc6f0e39000900e5dd1448103a9571f0eccd7d4e

cheers