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 <ndesaulni...@google.com>
> Fixes: 2efc7c085f05 ("powerpc/32: drop get_pteptr()")
> Signed-off-by: Christophe Leroy <christophe.le...@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 <natechancel...@gmail.com>
