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Subject[PATCH v1 2/2] selftests/landlock: Add layout1.refer_mount_root
Date
Add tests to check error codes when linking or renaming a mount root
directory. This previously triggered a kernel warning, but it is fixed
with the previous commit.

Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20240516181935.1645983-3-mic@digikod.net
---
tools/testing/selftests/landlock/fs_test.c | 45 ++++++++++++++++++++++
1 file changed, 45 insertions(+)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 6b5a9ff88c3d..7d063c652be1 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -35,6 +35,7 @@
* See https://sourceware.org/glibc/wiki/Synchronizing_Headers.
*/
#include <linux/fs.h>
+#include <linux/mount.h>

#include "common.h"

@@ -47,6 +48,13 @@ int renameat2(int olddirfd, const char *oldpath, int newdirfd,
}
#endif

+#ifndef open_tree
+int open_tree(int dfd, const char *filename, unsigned int flags)
+{
+ return syscall(__NR_open_tree, dfd, filename, flags);
+}
+#endif
+
#ifndef RENAME_EXCHANGE
#define RENAME_EXCHANGE (1 << 1)
#endif
@@ -2400,6 +2408,43 @@ TEST_F_FORK(layout1, refer_denied_by_default4)
layer_dir_s1d1_refer);
}

+/*
+ * Tests walking through a denied root mount.
+ */
+TEST_F_FORK(layout1, refer_mount_root_deny)
+{
+ const struct landlock_ruleset_attr ruleset_attr = {
+ .handled_access_fs = LANDLOCK_ACCESS_FS_MAKE_DIR,
+ };
+ int root_fd, ruleset_fd;
+
+ /* Creates a mount object from a non-mount point. */
+ set_cap(_metadata, CAP_SYS_ADMIN);
+ root_fd =
+ open_tree(AT_FDCWD, dir_s1d1,
+ AT_EMPTY_PATH | OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
+ clear_cap(_metadata, CAP_SYS_ADMIN);
+ ASSERT_LE(0, root_fd);
+
+ ruleset_fd =
+ landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+ ASSERT_LE(0, ruleset_fd);
+
+ ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+ ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
+ EXPECT_EQ(0, close(ruleset_fd));
+
+ /* Link denied by Landlock: EACCES. */
+ EXPECT_EQ(-1, linkat(root_fd, ".", root_fd, "does_not_exist", 0));
+ EXPECT_EQ(EACCES, errno);
+
+ /* renameat2() always returns EBUSY. */
+ EXPECT_EQ(-1, renameat2(root_fd, ".", root_fd, "does_not_exist", 0));
+ EXPECT_EQ(EBUSY, errno);
+
+ EXPECT_EQ(0, close(root_fd));
+}
+
TEST_F_FORK(layout1, reparent_link)
{
const struct rule layer1[] = {
--
2.45.0

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