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Shutemov" , Maya Gokhale , Johannes Weiner , Marty McFadden , Denis Plotnikov , Hugh Dickins , "Dr . David Alan Gilbert" , Jerome Glisse Subject: [PATCH v6 17/19] userfaultfd: wp: declare _UFFDIO_WRITEPROTECT conditionally Date: Thu, 20 Feb 2020 11:31:10 -0500 Message-Id: <20200220163112.11409-18-peterx@redhat.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200220163112.11409-1-peterx@redhat.com> References: <20200220163112.11409-1-peterx@redhat.com> MIME-Version: 1.0 X-MC-Unique: LLTh_VM7PCK426GwJ4KBjQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Only declare _UFFDIO_WRITEPROTECT if the user specified UFFDIO_REGISTER_MODE_WP and if all the checks passed. Then when the user registers regions with shmem/hugetlbfs we won't expose the new ioctl to them. Even with complete anonymous memory range, we'll only expose the new WP ioctl bit if the register mode has MODE_WP. Reviewed-by: Mike Rapoport Signed-off-by: Peter Xu --- fs/userfaultfd.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 6e878d23547c..e39fdec8a0b0 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1495,14 +1495,24 @@ static int userfaultfd_register(struct userfaultfd_= ctx *ctx, =09up_write(&mm->mmap_sem); =09mmput(mm); =09if (!ret) { +=09=09__u64 ioctls_out; + +=09=09ioctls_out =3D basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : +=09=09 UFFD_API_RANGE_IOCTLS; + +=09=09/* +=09=09 * Declare the WP ioctl only if the WP mode is +=09=09 * specified and all checks passed with the range +=09=09 */ +=09=09if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) +=09=09=09ioctls_out &=3D ~((__u64)1 << _UFFDIO_WRITEPROTECT); + =09=09/* =09=09 * Now that we scanned all vmas we can already tell =09=09 * userland which ioctls methods are guaranteed to =09=09 * succeed on this range. =09=09 */ -=09=09if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : -=09=09=09 UFFD_API_RANGE_IOCTLS, -=09=09=09 &user_uffdio_register->ioctls)) +=09=09if (put_user(ioctls_out, &user_uffdio_register->ioctls)) =09=09=09ret =3D -EFAULT; =09} out: --=20 2.24.1