On Mon, 17 Apr 2023 15:53:13 -0400 Peter Xu peterx@redhat.com wrote:
When we try to unshare a pinned page for a private hugetlb, uffd-wp bit can get lost during unsharing. Fix it by carrying it over.
This should be very rare, only if an unsharing happened on a private hugetlb page with uffd-wp protected (e.g. in a child which shares the same page with parent with UFFD_FEATURE_EVENT_FORK enabled).
What are the user-visible consequences of the bug?
Cc: linux-stable stable@vger.kernel.org
When proposing a backport, it's better to present the patch as a standalone thing, against current -linus. I'll then queue it in mm-hotfixes and shall send it upstream during this -rc cycle.
As presented, this patch won't go upstream until after 6.3 is released, and as it comes later in time, more backporting effort might be needed.
I can rework things if this fix is reasonably urgent (the "user-visible consequences" info is the guide). If not urgent, we can leave things as they are.