m68knommu: set ZERO_PAGE() to the allocated zeroed page
authorGreg Ungerer <gerg@linux-m68k.org>
Wed, 20 Apr 2022 13:27:47 +0000 (23:27 +1000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 14 Jun 2022 16:36:15 +0000 (18:36 +0200)
commit40426b4f08bc5a24ef7e95b52f637b23641d15d8
tree6ccd5b64fc47c0735dae8369322b3664311da65e
parent015e9831547e0c4ed167d194eb5da6cdccdc6792
m68knommu: set ZERO_PAGE() to the allocated zeroed page

[ 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