CVE-2022-48700 | Date: (C)2024-05-04 (M)2024-06-14 |
In the Linux kernel, the following vulnerability has been resolved:
vfio/type1: Unpin zero pages
There's currently a reference count leak on the zero page. We increment
the reference via pin_user_pages_remote(), but the page is later handled
as an invalid/reserved page, therefore it's not accounted against the
user and not unpinned by our put_pfn().
Introducing special zero page handling in put_pfn() would resolve the
leak, but without accounting of the zero page, a single user could
still create enough mappings to generate a reference count overflow.
The zero page is always resident, so for our purposes there's no reason
to keep it pinned. Therefore, add a loop to walk pages returned from
pin_user_pages_remote() and unpin any zero pages.
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