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Thu, 29 Oct 2026 15:11:41 -0700 (PDT) From: "Jose A. Perez de Azpillaga" To: Andrew Morton , Mike Rapoport , David Hildenbrand , Shuah Khan , Peter Xu Cc: Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Muchun Song , Oscar Salvador , "Jose A. Perez de Azpillaga" Subject: [PATCH 2/2] selftests/mm: add a uffd test for re-registering during UFFDIO_COPY Date: Thu, 29 Oct 2026 23:11:02 +0100 Message-ID: <20261029221129.89068-3-azpijr@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261029221129.89068-1-azpijr@gmail.com> References: <20261029221129.89068-1-azpijr@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: D98871C0006 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: dyguwzops4jedq8epc3qpp7oep7bzs5h X-HE-Tag: 1793311902-712292 X-HE-Meta: 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 lo3ytWMu h/tRKfnZx6Zbm8Fq8KN5xuKl5RVrFIKfTNexNvmrTwusNfSXNEy60VBk/DFrKDsJmPrUyQujW1Ds8wXyI6u8LM5kqlurZlfI/UrsB4ne/N/lic08Q1wz6epM4WYrF7UllPNKHVkdS69mk1HWvfzm8TBhQauAIVVynBllqeMls2iVvWOlmr5+I6FNsmgDtYM38rgk9fjU+l1l1MlXxMAzEwcE83bZbb1rYkgw7ZCknme2/lYGom6/rkMV/OxNeyo6HlBglCnHpMFaPyqpFOAMxszT0iBknLO+alMtfo7afsn9rx97qtV7em5kj10d3o1A/U7WEhKdMve5v1njQacKFhf+sVMHm+JLH+E/WldY1EIU5ILESH41Mj0+j8Tab/fCldOluU9fUUtXF+hgwkHzrvSXc5437krwLKsJytLAiA3bTcm4dMLkKi6MNvaWVblyApOM2LBJep/lMPmc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Re-register the destination without WP while a UFFDIO_COPY_MODE_WP copy waits for its source page, then check that the copy fails with -EINVAL and leaves no uffd-wp bit behind. This covers both the hugetlb and the non-hugetlb UFFDIO_COPY retry. Signed-off-by: Jose A. Perez de Azpillaga --- tools/testing/selftests/mm/uffd-unit-tests.c | 105 +++++++++++++++++++ 1 file changed, 105 insertions(+) diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index 2a97ba1d6feb..8a7efaa7b3ac 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -375,6 +375,104 @@ static void uffd_wp_unpopulated_test(uffd_global_test_opts_t *gopts, uffd_test_a uffd_test_pass(); } +struct wp_copy_args { + uffd_global_test_opts_t *gopts; + char *src; + __s64 copy; +}; + +static void *wp_copy_thread(void *data) +{ + struct wp_copy_args *args = data; + struct uffdio_copy copy = { + .dst = (unsigned long)args->gopts->area_dst, + .src = (unsigned long)args->src, + .len = args->gopts->page_size, + .mode = UFFDIO_COPY_MODE_WP, + }; + + ioctl(args->gopts->uffd, UFFDIO_COPY, ©); + args->copy = copy.copy; + + return NULL; +} + +/* + * UFFDIO_COPY drops its locks to fault in the source page. Re-register the + * destination without WP while it waits there: the MODE_WP copy must then + * fail instead of leaving a uffd-wp bit in a VMA that no longer has WP. + */ +static void uffd_wp_copy_reregister_test(uffd_global_test_opts_t *gopts, + uffd_test_args_t *args) +{ + struct uffdio_api api = { .api = UFFD_API }; + struct wp_copy_args copy_args = { .gopts = gopts }; + unsigned long len = gopts->page_size; + struct uffdio_zeropage zeropage; + struct uffd_msg msg; + struct pollfd pfd; + pthread_t thread; + uint64_t value; + int pagemap_fd; + int src_uffd; + + /* The source fault comes from the kernel, so no UFFD_USER_MODE_ONLY */ + src_uffd = uffd_open(O_CLOEXEC); + if (src_uffd < 0) { + uffd_test_skip("cannot open a kernel-mode userfaultfd"); + return; + } + if (ioctl(src_uffd, UFFDIO_API, &api)) + err("UFFDIO_API failed"); + + copy_args.src = mmap(NULL, len, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (copy_args.src == MAP_FAILED) + err("mmap() failed"); + + if (uffd_register(src_uffd, copy_args.src, len, true, false, false)) + err("register src failed"); + if (uffd_register(gopts->uffd, gopts->area_dst, len, true, true, false)) + err("register dst failed"); + + if (pthread_create(&thread, NULL, wp_copy_thread, ©_args)) + err("pthread_create() failed"); + + /* Wait until UFFDIO_COPY blocks on the source page */ + pfd = (struct pollfd){ .fd = src_uffd, .events = POLLIN }; + if (poll(&pfd, 1, 10000) != 1) + err("no fault on the source page"); + if (read(src_uffd, &msg, sizeof(msg)) != sizeof(msg)) + err("read() failed"); + + if (uffd_unregister(gopts->uffd, gopts->area_dst, len)) + err("unregister dst failed"); + if (uffd_register(gopts->uffd, gopts->area_dst, len, true, false, false)) + err("re-register dst failed"); + + zeropage.range.start = (unsigned long)copy_args.src; + zeropage.range.len = len; + zeropage.mode = 0; + if (ioctl(src_uffd, UFFDIO_ZEROPAGE, &zeropage)) + err("UFFDIO_ZEROPAGE failed"); + + if (pthread_join(thread, NULL)) + err("pthread_join() failed"); + + if (copy_args.copy != -EINVAL) + err("UFFDIO_COPY returned %lld, expected %d", + (long long)copy_args.copy, -EINVAL); + + pagemap_fd = pagemap_open(); + value = pagemap_get_entry(pagemap_fd, gopts->area_dst); + pagemap_check_wp(value, false); + close(pagemap_fd); + + munmap(copy_args.src, len); + close(src_uffd); + uffd_test_pass(); +} + static void uffd_wp_fork_test_common(uffd_global_test_opts_t *gopts, uffd_test_args_t *args, bool with_event) { @@ -2403,6 +2501,13 @@ uffd_test_case_t uffd_tests[] = { .uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP | UFFD_FEATURE_WP_UNPOPULATED, }, + { + .name = "wp-copy-reregister", + .uffd_fn = uffd_wp_copy_reregister_test, + .mem_targets = MEM_ALL, + .uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP | + UFFD_FEATURE_WP_HUGETLBFS_SHMEM, + }, { .name = "minor", .uffd_fn = uffd_minor_test, -- 2.55.0