On 11.09.22 11:59, Pasha Tatashin wrote:
From: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
The zero page should remain all zero, so that it can be mapped as
read-only for read faults of memory that should be zeroed. If it is ever
mapped writable to userspace, it could become non-zero and so other apps
would unexpectedly get non-zero data. So the zero page should never be
mapped writable to userspace. Check for this condition in
page_table_check_set().
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
---
mm/page_table_check.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index e2062748791a..665ece0d55d4 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -102,6 +102,8 @@ static void page_table_check_set(struct mm_struct *mm, unsigned long addr,
if (!pfn_valid(pfn))
return;
+ BUG_ON(is_zero_pfn(pfn) && rw);
We most probably don't want that:
https://lkml.kernel.org/r/20220923113426.52871-2-david@xxxxxxxxxx
--
Thanks,
David / dhildenb
