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[184.145.104.227]) by smtp.gmail.com with ESMTPSA id 191sm897459qkk.31.2021.04.28.15.51.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Apr 2021 15:51:19 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Mike Kravetz , peterx@redhat.com, Mike Rapoport , Axel Rasmussen , Andrea Arcangeli , Hugh Dickins , "Kirill A . Shutemov" , Andrew Morton , Jerome Glisse Subject: [PATCH 4/6] mm/userfaultfd: Fail uffd-wp registeration if not supported Date: Wed, 28 Apr 2021 18:50:28 -0400 Message-Id: <20210428225030.9708-5-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210428225030.9708-1-peterx@redhat.com> References: <20210428225030.9708-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We should fail uffd-wp registration immediately if the arch does not even have CONFIG_HAVE_ARCH_USERFAULTFD_WP defined. That'll block also relevant ioctls on e.g. UFFDIO_WRITEPROTECT because that'll check against VM_UFFD_WP, which can only be applied with a success registration. Remove the WP feature bit too for those archs when handling UFFDIO_API ioctl. Signed-off-by: Peter Xu --- fs/userfaultfd.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 14f92285d04f8..5dd78238cc156 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1304,8 +1304,12 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, vm_flags = 0; if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) vm_flags |= VM_UFFD_MISSING; - if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) + if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { +#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP + goto out; +#endif vm_flags |= VM_UFFD_WP; + } if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) { #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR goto out; @@ -1942,6 +1946,9 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, uffdio_api.features = UFFD_API_FEATURES; #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR uffdio_api.features &= ~UFFD_FEATURE_MINOR_HUGETLBFS; +#endif +#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP + uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; #endif uffdio_api.ioctls = UFFD_API_IOCTLS; ret = -EFAULT; -- 2.26.2