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@goog... 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 fc3a96c77bd8..12f673707d4b 100644 --- a/arch/m68k/include/asm/pgtable_no.h +++ b/arch/m68k/include/asm/pgtable_no.h @@ -42,7 +42,8 @@ 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.