| From 5b7e08f233c555ecb2d932d3479d6f251e5ae9b8 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 20 Apr 2022 23:27:47 +1000 |
| Subject: m68knommu: set ZERO_PAGE() to the allocated zeroed page |
| |
| From: Greg Ungerer <gerg@linux-m68k.org> |
| |
| [ Upstream commit dc068f46217970d9516f16cd37972a01d50dc055 ] |
| |
| The non-MMU m68k pagetable ZERO_PAGE() macro is being set to the |
| somewhat non-sensical value of "virt_to_page(0)". The zeroth page |
| is not in any way guaranteed to be a page full of "0". So the result |
| is that ZERO_PAGE() will almost certainly contain random values. |
| |
| We already allocate a real "empty_zero_page" in the mm setup code shared |
| between MMU m68k and non-MMU m68k. It is just not hooked up to the |
| ZERO_PAGE() macro for the non-MMU m68k case. |
| |
| Fix ZERO_PAGE() to use the allocated "empty_zero_page" pointer. |
| |
| I am not aware of any specific issues caused by the old code. |
| |
| Link: https://lore.kernel.org/linux-m68k/2a462b23-5b8e-bbf4-ec7d-778434a3b9d7@google.com/T/#t |
| Reported-by: Hugh Dickens <hughd@google.com> |
| Signed-off-by: Greg Ungerer <gerg@linux-m68k.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/m68k/include/asm/pgtable_no.h | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| diff --git a/arch/m68k/include/asm/pgtable_no.h b/arch/m68k/include/asm/pgtable_no.h |
| index ac7d87a02335..269443e1084b 100644 |
| --- a/arch/m68k/include/asm/pgtable_no.h |
| +++ b/arch/m68k/include/asm/pgtable_no.h |
| @@ -41,7 +41,8 @@ extern void paging_init(void); |
| * ZERO_PAGE is a global shared page that is always zero: used |
| * for zero-mapped memory areas etc.. |
| */ |
| -#define ZERO_PAGE(vaddr) (virt_to_page(0)) |
| +extern void *empty_zero_page; |
| +#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page)) |
| |
| /* |
| * No page table caches to initialise. |
| -- |
| 2.35.1 |
| |
