On 10.11.20 10:36, Alexander Gordeev wrote:
If for whatever reason the sub-PMD region to be used is less
than struct page size (e.g in the future), then it is possible
to overwrite beyond the region size.
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
---
arch/s390/mm/vmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index 56ab9bb770f3a..d7f25884061f4 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -91,13 +91,15 @@ static void vmemmap_flush_unused_pmd(void)
static void __vmemmap_use_sub_pmd(unsigned long start, unsigned long end)
{
+ unsigned long size = min(end - start, sizeof(struct page));
+
/*
* As we expect to add in the same granularity as we remove, it's
* sufficient to mark only some piece used to block the memmap page from
* getting removed (just in case the memmap never gets initialized,
* e.g., because the memory block never gets onlined).
*/
- memset(__va(start), 0, sizeof(struct page));
+ memset(__va(start), 0, size);
}
static void vmemmap_use_sub_pmd(unsigned long start, unsigned long end)
I don't really see a need for that. Can you spell out one possible
configuration that would trigger that in the future? It's sounds very
unlikely and I have the feeling there might be more to change at other
points.
--
Thanks,
David / dhildenb
