linux-kernel - [PATCH v10 2/6] userfaultfd: update documentation to describe UFFD_FEATURE_WP

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Thu,  2 Feb 2023 16:29:11 +0500
From:   Muhammad Usama Anjum <usama.anjum@...labora.com>
To:     Peter Xu <peterx@...hat.com>, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <emmir@...gle.com>,
        Andrei Vagin <avagin@...il.com>,
        Danylo Mocherniuk <mdanylo@...gle.com>,
        Paul Gofman <pgofman@...eweavers.com>,
        Cyrill Gorcunov <gorcunov@...il.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Yun Zhou <yun.zhou@...driver.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Alex Sierra <alex.sierra@....com>,
        Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Matthew Wilcox <willy@...radead.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Mike Rapoport <rppt@...nel.org>, Nadav Amit <namit@...are.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        Greg KH <gregkh@...uxfoundation.org>, kernel@...labora.com
Subject: [PATCH v10 2/6] userfaultfd: update documentation to describe UFFD_FEATURE_WP_ASYNC

Explain the difference created by UFFD_FEATURE_WP_ASYNC to the write
protection (UFFDIO_WRITEPROTECT_MODE_WP) mode.

Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
---
 Documentation/admin-guide/mm/userfaultfd.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst
index 83f31919ebb3..4747e7bd5b26 100644
--- a/Documentation/admin-guide/mm/userfaultfd.rst
+++ b/Documentation/admin-guide/mm/userfaultfd.rst
@@ -221,6 +221,13 @@ former will have ``UFFD_PAGEFAULT_FLAG_WP`` set, the latter
 you still need to supply a page when ``UFFDIO_REGISTER_MODE_MISSING`` was
 used.
 
+If ``UFFD_FEATURE_WP_ASYNC`` is set while calling ``UFFDIO_API`` ioctl, the
+behaviour of ``UFFDIO_WRITEPROTECT_MODE_WP`` changes such that faults for
+anon and shmem are resolved automatically by the kernel instead of sending
+the message to the userfaultfd. The hugetlb isn't supported. The ``pagemap``
+file can be read to find which pages have ``PM_UFFD_WP`` flag set which
+means they are write-protected.
+
 QEMU/KVM
 ========
 
-- 
2.30.2