[LTP] [PATCH v12 2/8] fs/acl: Add ACL mask interaction tests
Sachin Sant
sachinp@linux.ibm.com
Tue Jun 16 06:54:08 CEST 2026
Add acl_mask01 test to verify that ACL_MASK correctly restricts
permissions for ACL_USER, ACL_GROUP, and ACL_GROUP_OBJ entries.
Test validates ACL_USER, ACL_GROUP, and ACL_GROUP_OBJ
permissions are restricted by mask
Each test verifies that:
- With mask set to rwx, access is granted
- With mask cleared (---), access is denied with EACCES
The test uses direct xattr manipulation via acl_lib.h helpers and
arbitrary UIDs without requiring actual user creation, testing only
the kernel ACL implementation
Suggested-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Sachin Sant <sachinp@linux.ibm.com>
---
No changes in v11 and v12
V10 changes:
- Collapsed into a single parametrized test function driven
by a struct tcase array.
- v9 link https://lore.kernel.org/ltp/20260615052953.18183-1-sachinp@linux.ibm.com/T/#t
V9 changes:
- Use RST manpage formatted documentation
- v8 link https://lore.kernel.org/ltp/20260613090543.78643-1-sachinp@linux.ibm.com/T/#t
V8 changes:
- No change
V7 changes:
- No change
V6 changes:
- Adds proper portability guards for systems without xattr support
- Removed error checking for acl_add_entry() into library functions
- v5 link https://lore.kernel.org/ltp/20260608092200.92827-1-sachinp@linux.ibm.com/T/#t
V5 changes:
- Switch to kernel only test validation to remove dependency on libacl
and useradd/del commands.
- v3 link https://lore.kernel.org/ltp/20260604065417.25924-1-sachinp@linux.ibm.com/T/#t
V4 changes:
- No change
V3 changes:
- Updated copyright header as per LTP format.
- v1 link https://lore.kernel.org/ltp/20260602121958.27494-1-sachinp@linux.ibm.com/T/#t
V2 changes:
- No change
V1 changes:
- Use HAVE_LIBACL guards in .c code
- Report TCONF when libacl is not available
- rfc link https://lore.kernel.org/ltp/477836fd-80c8-4168-bfe6-00b374bb2534@linux.ibm.com/T/#t
---
runtest/fs | 1 +
testcases/kernel/fs/acl/.gitignore | 1 +
testcases/kernel/fs/acl/acl_mask01.c | 175 +++++++++++++++++++++++++++
3 files changed, 177 insertions(+)
create mode 100644 testcases/kernel/fs/acl/acl_mask01.c
diff --git a/runtest/fs b/runtest/fs
index 2a878744b..69ecb8647 100644
--- a/runtest/fs
+++ b/runtest/fs
@@ -90,3 +90,4 @@ squashfs01 squashfs01
# Run the acl tests
acl_user_obj01 acl_user_obj01
+acl_mask01 acl_mask01
diff --git a/testcases/kernel/fs/acl/.gitignore b/testcases/kernel/fs/acl/.gitignore
index d9c46db11..bfcdee93d 100644
--- a/testcases/kernel/fs/acl/.gitignore
+++ b/testcases/kernel/fs/acl/.gitignore
@@ -1 +1,2 @@
/acl_user_obj01
+/acl_mask01
diff --git a/testcases/kernel/fs/acl/acl_mask01.c b/testcases/kernel/fs/acl/acl_mask01.c
new file mode 100644
index 000000000..8803e91eb
--- /dev/null
+++ b/testcases/kernel/fs/acl/acl_mask01.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 IBM
+ *
+ * Original shell test by Kai Zhao (ltcd3@cn.ibm.com)
+ * Converted to C by Sachin Sant <sachinp@linux.ibm.com>
+ */
+
+/*\
+ * Test ACL mask interaction with named users and groups using direct xattr
+ * manipulation.
+ *
+ * Verify that ACL_MASK correctly restricts permissions for:
+ * - ACL_USER (named user) entries
+ * - ACL_GROUP (named group) entries
+ * - ACL_GROUP_OBJ (group owner) entries
+ *
+ * The mask acts as an upper bound on permissions for these entry types.
+ * Even if an entry grants full permissions, the mask can restrict them.
+ * ACL_USER_OBJ and ACL_OTHER are not affected by the mask.
+ *
+ * This test uses arbitrary UIDs without creating actual users, testing
+ * only the kernel ACL implementation.
+ *
+ * [Algorithm]
+ *
+ * The test uses a parametrized approach with three test cases, one for each
+ * entry type (ACL_USER, ACL_GROUP, ACL_GROUP_OBJ). For each test case:
+ *
+ * - Set up ACL with full permissions (rwx) for the entry type
+ * - Set mask to allow full permissions (rwx)
+ * - Verify access is granted
+ * - Clear mask permissions (---)
+ * - Verify access is denied despite entry having full permissions
+ */
+
+#include "acl_lib.h"
+
+#ifdef HAVE_SYS_XATTR_H
+
+#define TEST_UID 1000
+#define TEST_GID 1000
+#define USER2_UID 2000
+#define USER2_GID 2000
+#define USER3_UID 3000
+#define USER3_GID 3000
+
+static struct tcase {
+ uint16_t tag;
+ uid_t uid;
+ gid_t gid;
+ uid_t owner_uid;
+ gid_t owner_gid;
+ const char *desc;
+} tcases[] = {
+ {ACL_USER, USER3_UID, USER3_GID, TEST_UID, TEST_GID,
+ "ACL_USER with mask"},
+ {ACL_GROUP, USER2_UID, USER2_GID, TEST_UID, TEST_GID,
+ "ACL_GROUP with mask"},
+ {ACL_GROUP_OBJ, USER2_UID, USER2_GID, TEST_UID, USER2_GID,
+ "ACL_GROUP_OBJ with mask"},
+};
+
+/*
+ * Test ACL mask interaction with different entry types.
+ * The mask acts as an upper bound on permissions for ACL_USER,
+ * ACL_GROUP, and ACL_GROUP_OBJ entries.
+ */
+static void run(unsigned int n)
+{
+ struct tcase *tc = &tcases[n];
+ struct acl *acl;
+
+ tst_res(TINFO, "Testing %s", tc->desc);
+ reset_test_path();
+
+ SAFE_CHOWN(TESTDIR, tc->owner_uid, tc->owner_gid);
+ SAFE_CHMOD(TESTDIR, 0550);
+
+ acl = acl_init();
+
+ /* Set up ACL with full permissions for the entry type */
+ acl_add_entry(acl, ACL_USER_OBJ,
+ ACL_READ | ACL_WRITE | ACL_EXECUTE, 0);
+
+ if (tc->tag == ACL_USER) {
+ acl_add_entry(acl, ACL_USER,
+ ACL_READ | ACL_WRITE | ACL_EXECUTE, tc->uid);
+ acl_add_entry(acl, ACL_GROUP_OBJ, 0, 0);
+ } else if (tc->tag == ACL_GROUP) {
+ acl_add_entry(acl, ACL_GROUP_OBJ, 0, 0);
+ acl_add_entry(acl, ACL_GROUP,
+ ACL_READ | ACL_WRITE | ACL_EXECUTE, tc->gid);
+ } else {
+ acl_add_entry(acl, ACL_GROUP_OBJ,
+ ACL_READ | ACL_WRITE | ACL_EXECUTE, 0);
+ }
+
+ acl_add_entry(acl, ACL_MASK,
+ ACL_READ | ACL_WRITE | ACL_EXECUTE, 0);
+ acl_add_entry(acl, ACL_OTHER, 0, 0);
+
+ if (acl_set_file(TESTDIR, ACL_TYPE_ACCESS, acl) < 0) {
+ if (errno == EOPNOTSUPP) {
+ acl_free(acl);
+ tst_brk(TCONF | TERRNO, "ACL not supported");
+ }
+ acl_free(acl);
+ tst_brk(TBROK | TERRNO, "ACL setup failed");
+ }
+
+ acl_free(acl);
+
+ /* Verify access is granted with mask=rwx */
+ try_create_as(tc->uid, tc->gid, 0644, 0);
+
+ cleanup_testfile();
+
+ /* Clear mask permissions */
+ acl = acl_get_file(TESTDIR, ACL_TYPE_ACCESS);
+ if (!acl)
+ tst_brk(TBROK | TERRNO, "acl_get_file failed");
+
+ if (acl_set_mask_perms(acl, 0) < 0) {
+ acl_free(acl);
+ tst_brk(TBROK | TERRNO, "acl_set_mask_perms failed");
+ }
+
+ if (acl_set_file(TESTDIR, ACL_TYPE_ACCESS, acl) < 0) {
+ acl_free(acl);
+ tst_brk(TBROK | TERRNO, "acl_set_file failed");
+ }
+
+ acl_free(acl);
+
+ /* Verify access is denied with mask=--- */
+ try_create_as(tc->uid, tc->gid, 0644, EACCES);
+
+ /* Restore ownership for ACL_GROUP_OBJ case */
+ if (tc->tag == ACL_GROUP_OBJ)
+ SAFE_CHOWN(TESTDIR, TEST_UID, TEST_GID);
+}
+
+static void setup(void)
+{
+ reset_test_path();
+}
+
+static void cleanup(void)
+{
+ cleanup_test_paths();
+}
+
+static struct tst_test test = {
+ .test = run,
+ .tcnt = ARRAY_SIZE(tcases),
+ .setup = setup,
+ .cleanup = cleanup,
+ .needs_root = 1,
+ .mount_device = 1,
+ .mntpoint = MNTPOINT,
+ .forks_child = 1,
+ .filesystems = (struct tst_fs[]) {
+ {.type = "ext2", .mnt_data = "acl"},
+ {.type = "ext3", .mnt_data = "acl"},
+ {.type = "ext4", .mnt_data = "acl"},
+ {.type = "xfs"},
+ {.type = "btrfs"},
+ {}
+ }
+};
+
+#else
+ TST_TEST_TCONF("sys/xattr.h is not available");
+#endif
--
2.39.1
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