From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-bc0f.mail.infomaniak.ch (smtp-bc0f.mail.infomaniak.ch [45.157.188.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F3991F936 for ; Thu, 17 Sep 2026 14:55:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.157.188.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789656990; cv=none; b=VQGcC/lE5uQHU9+KbtYJePrMuQz+Ch0mkW1EKGh5EaGgwdPfhP7RABQXDsCWDKTHDPH4QBjqdvmWAtEmipL3MO1Kj3SatMjhznkuCXkV24OuyVSt47lcP8CK2YJdamo9xbsp8awP6Vs/X9ZnBo57wMYvVWJ34+nXwXF3ZnT226I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789656990; c=relaxed/simple; bh=5nE39/imSlDB2IgcyOzV3DtB3+adDOPOTTkPE7I5Q3E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=PTycNq442GANvC2uP8TzpXNQTQEZW18DE70A0GtdzylNjDH/VTGxISBrR2aFzBXOFS79karQrz8Zb1fel/vu4bnAcc9FRrgSthCGWi/axYSesaXJ9lbpZ+FvUqOzBqzMQ15ESDV2NfmV3/IVf7QyNuNJ9r42ZLhcQDKQJ02z3XI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=tGoWdSZ/; arc=none smtp.client-ip=45.157.188.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="tGoWdSZ/" Received: from smtp-3-0001.mail.infomaniak.ch (smtp-3-0001.mail.infomaniak.ch [10.4.36.108]) by smtp-4-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4hlzMg5hM5zSdN; Thu, 17 Sep 2026 16:55:43 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digikod.net; s=20191114; t=1789656943; bh=iIriynrEu5LwJNNlh0oydDdRqnA/sdfPPXQmxmJmFHs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tGoWdSZ/WeEXt6dtuIqJwoakoP9xiqamZ5GKsP1tn667tVF/NIL6x7m76f7jx8zut xgfpTvZ6rW/SPsU4OYSjnfmGdBCeTF+lFG9l58WBrKydQG3bh40goqCWnYQthMqcCv rS+n5kmPJeslje/7bJiVMP/iqqE4CjUPN+CsSXjQ= Received: from unknown by smtp-3-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4hlzMf3yQRz14t; Thu, 17 Sep 2026 16:55:42 +0200 (CEST) From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= To: stable@vger.kernel.org Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Greg Kroah-Hartman , =?utf-8?q?G=C3=BCnther_Noack?= , Christian Brauner , John Johansen , James Morris , "Serge E. Hallyn" , Kentaro Takeda , Tetsuo Handa , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Al Viro , Jann Horn , Kees Cook , Konstantin Meskhidze , Paul Moore , Shuah Khan , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 5.15.y 2/2] selftests/landlock: Add tests for whiteout object creation Date: Thu, 17 Sep 2026 16:55:22 +0200 Message-ID: <88432dfe86f2aaa9ae499587fd7acff9d34a338b.1789655723.git.mic@digikod.net> In-Reply-To: <2026090319-sprinkler-mandolin-e566@gregkh> References: <2026090319-sprinkler-mandolin-e566@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Infomaniak-Routing: alpha From: Günther Noack [ Upstream commit ee890889b30b22f9a21636061def7a04e4f89380 ] Add tests to check that whiteout object creation is guarded by LANDLOCK_ACCESS_FS_MAKE_REG, in the cases where these are created from userspace: * Conventional creation with mknod() * Linking or renaming an existing whiteout object * renameat2() with RENAME_WHITEOUT, which creates a new whiteout object in the source location * renameat2() with RENAME_EXCHANGE, with one of the renamed objects being a whiteout object Signed-off-by: Günther Noack Link: https://patch.msgid.link/20260813093157.1436894-4-gnoack@google.com [mic: Update commit message as requested] Signed-off-by: Mickaël Salaün [mic: Backport: add enforce_fs() and the missing s3 fixture paths, and adapt tests to ABI 1 without REFER] Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 150 +++++++++++++++++++++ 1 file changed, 150 insertions(+) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 47fc4392f412..f5c965e9aa80 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -62,6 +62,8 @@ static const char dir_s3d1[] = TMP_DIR "/s3d1"; /* dir_s3d2 is a mount point. */ static const char dir_s3d2[] = TMP_DIR "/s3d1/s3d2"; static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3"; +static const char file1_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3/f1"; +static const char file2_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3/f2"; /* * layout1 hierarchy: @@ -249,6 +251,7 @@ static void create_layout1(struct __test_metadata *const _metadata) clear_cap(_metadata, CAP_SYS_ADMIN); ASSERT_EQ(0, mkdir(dir_s3d3, 0700)); + create_file(_metadata, file1_s3d3); } static void remove_layout1(struct __test_metadata *const _metadata) @@ -265,6 +268,8 @@ static void remove_layout1(struct __test_metadata *const _metadata) EXPECT_EQ(0, remove_path(file1_s2d2)); EXPECT_EQ(0, remove_path(file1_s2d1)); + EXPECT_EQ(0, remove_path(file2_s3d3)); + EXPECT_EQ(0, remove_path(file1_s3d3)); EXPECT_EQ(0, remove_path(dir_s3d3)); set_cap(_metadata, CAP_SYS_ADMIN); umount(dir_s3d2); @@ -595,6 +600,27 @@ static void enforce_ruleset(struct __test_metadata *const _metadata, } } +static void enforce_fs(struct __test_metadata *const _metadata, + const __u64 access_fs, const struct rule rules[]) +{ + int ruleset_fd; + + if (rules) { + ruleset_fd = create_ruleset(_metadata, access_fs, rules); + } else { + const struct landlock_ruleset_attr ruleset_attr = { + .handled_access_fs = access_fs, + }; + + ruleset_fd = landlock_create_ruleset(&ruleset_attr, + sizeof(ruleset_attr), 0); + ASSERT_LE(0, ruleset_fd); + } + + enforce_ruleset(_metadata, ruleset_fd); + EXPECT_EQ(0, close(ruleset_fd)); +} + TEST_F_FORK(layout1, proc_nsfs) { const struct rule rules[] = { @@ -1941,6 +1967,118 @@ TEST_F_FORK(layout1, rename_file) RENAME_EXCHANGE)); } +TEST_F_FORK(layout1, rename_whiteout_denied) +{ + /* The affected file is a FIFO. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + + /* Deny MAKE_REG, but allow MAKE_FIFO. */ + enforce_fs(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, NULL); + + /* + * Try to rename a file with RENAME_WHITEOUT. + * file1_s3d3 is in dir_s3d2 (tmpfs), so it supports RENAME_WHITEOUT. + * Denied, because whiteout creation is guarded with MAKE_REG. + */ + EXPECT_EQ(-1, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, file2_s3d3, + RENAME_WHITEOUT)); + EXPECT_EQ(EACCES, errno); +} + +static bool is_whiteout(const char *const path) +{ + struct stat st; + + if (stat(path, &st) == -1) + return false; + + return S_ISCHR(st.st_mode) && st.st_rdev == makedev(0, 0); +} + +static bool is_fifo(const char *const path) +{ + struct stat st; + + return stat(path, &st) == 0 && S_ISFIFO(st.st_mode); +} + +TEST_F_FORK(layout1, rename_whiteout_allowed) +{ + const struct rule rules[] = { + { + .path = dir_s3d3, + .access = LANDLOCK_ACCESS_FS_MAKE_REG, + }, + {}, + }; + + /* The affected file is a FIFO. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + + /* Allow MAKE_REG below dir_s3d3. */ + enforce_fs(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, rules); + + /* + * Rename a file with RENAME_WHITEOUT within the same directory. + * Allowed, because MAKE_REG is granted for the whiteout object which + * gets created in the source location. + */ + EXPECT_EQ(0, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, file2_s3d3, + RENAME_WHITEOUT)); + + /* A whiteout object took the place of the moved FIFO. */ + EXPECT_TRUE(is_whiteout(file1_s3d3)); + EXPECT_TRUE(is_fifo(file2_s3d3)); +} + +TEST_F_FORK(layout1, rename_whiteout_exchange_denied) +{ + const char *const whiteout_s3d3 = file2_s3d3; + + /* The exchanged files are a FIFO and an existing whiteout object. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + ASSERT_EQ(0, mknod(whiteout_s3d3, S_IFCHR | 0600, makedev(0, 0))); + + /* Deny MAKE_REG, but allow MAKE_FIFO. */ + enforce_fs(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, NULL); + + /* Exchanging the whiteout object is denied without MAKE_REG. */ + EXPECT_EQ(-1, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, whiteout_s3d3, + RENAME_EXCHANGE)); + EXPECT_EQ(EACCES, errno); +} + +TEST_F_FORK(layout1, rename_whiteout_exchange_allowed) +{ + const char *const whiteout_s3d3 = file2_s3d3; + const struct rule rules[] = { + { + .path = dir_s3d3, + .access = LANDLOCK_ACCESS_FS_MAKE_REG, + }, + {}, + }; + + /* The exchanged files are a FIFO and an existing whiteout object. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + ASSERT_EQ(0, mknod(whiteout_s3d3, S_IFCHR | 0600, makedev(0, 0))); + + /* Allow MAKE_REG below dir_s3d3. */ + enforce_fs(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, rules); + + /* Exchanging the whiteout object is allowed with MAKE_REG. */ + EXPECT_EQ(0, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, whiteout_s3d3, + RENAME_EXCHANGE)); + + /* The FIFO and the whiteout object swapped places. */ + EXPECT_TRUE(is_whiteout(file1_s3d3)); + EXPECT_TRUE(is_fifo(whiteout_s3d3)); +} + TEST_F_FORK(layout1, rename_dir) { const struct rule rules[] = { @@ -2128,6 +2266,18 @@ TEST_F_FORK(layout1, make_char) makedev(1, 3)); } +TEST_F_FORK(layout1, make_whiteout) +{ + /* + * Creates a whiteout object (creation guarded by MAKE_REG). + * + * Contrary to the other character devices, this does not require + * CAP_MKNOD, cf. vfs_mknod(). + */ + test_make_file(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, S_IFCHR, + makedev(0, 0)); +} + TEST_F_FORK(layout1, make_block) { /* Creates a /dev/loop0 device. */