Commit 166f3ecc authored May 12, 2022 by Peter Xu Committed by Andrew Morton May 13, 2022

mm/hugetlb: hook page faults for uffd write protection

Hook up hugetlbfs_fault() with the capability to handle userfaultfd-wp
faults.

We do this slightly earlier than hugetlb_cow() so that we can avoid taking
some extra locks that we definitely don't need.

Link: https://lkml.kernel.org/r/20220405014901.14590-1-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 229f3fa7

mm/hugetlb.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -5737,6 +5737,26 @@ vm_fault_t hugetlb_fault(struct mm_struct mm, struct vm_area_struct vma,
		if (unlikely(!pte_same(entry, huge_ptep_get(ptep))))
		goto out_ptl;

		/* Handle userfault-wp first, before trying to lock more pages */
		if (userfaultfd_wp(vma) && huge_pte_uffd_wp(huge_ptep_get(ptep)) &&
		(flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
		struct vm_fault vmf = {
		.vma = vma,
		.address = haddr,
		.real_address = address,
		.flags = flags,
		};

		spin_unlock(ptl);
		if (pagecache_page) {
		unlock_page(pagecache_page);
		put_page(pagecache_page);
		}
		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
		i_mmap_unlock_read(mapping);
		return handle_userfault(&vmf, VM_UFFD_WP);
		}

		/*
		* hugetlb_wp() requires page locks of pte_page(entry) and
		* pagecache_page, so here we need take the former one