linux-kernel - [PATCH v2 16/24] hugetlb/userfaultfd: Hook page faults for uffd write protection

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210427161317.50682-17-peterx@redhat.com>
Date:   Tue, 27 Apr 2021 12:13:09 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Nadav Amit <nadav.amit@...il.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>, peterx@...hat.com,
        Jerome Glisse <jglisse@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>
Subject: [PATCH v2 16/24] hugetlb/userfaultfd: 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.

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/hugetlb.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 629aa4c2259c8..8e234ee9a15e2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4802,6 +4802,25 @@ 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_pte_wp(vma, huge_ptep_get(ptep)) &&
+	    (flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
+		struct vm_fault vmf = {
+			.vma = vma,
+			.address = haddr,
+			.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_cow() requires page locks of pte_page(entry) and
 	 * pagecache_page, so here we need take the former one
-- 
2.26.2