Messages in this thread | | | Date | Mon, 26 Sep 2022 10:26:52 +0200 | Subject | Re: [PATCH 1/3] mm/page_table_check: Check writable zero page in page table check | From | David Hildenbrand <> |
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On 11.09.22 11:59, Pasha Tatashin wrote: > From: Rick Edgecombe <rick.p.edgecombe@intel.com> > > 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@intel.com> > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> > --- > 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@redhat.com
-- Thanks,
David / dhildenb
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