selftests/filesystems: add basic fscontext log tests

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/20250807-fscontext-log-cleanups-v3-2-8d91d6242dc3@cyphar.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/filesystems/.gitignore b/tools/testing/selftests/filesystems/.gitignore
index fcbdb1297e24e85ac6439e31d70f7d4e504ef519..64ac0dfa46b7ef32fd5c2acdc87eb5ec9dcc01ec 100644 (file)
--- a/tools/testing/selftests/filesystems/.gitignore
+++ b/tools/testing/selftests/filesystems/.gitignore
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 dnotify_test
 devpts_pts
+fclog
 file_stressor
 anon_inode_test
 kernfs_test

diff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/selftests/filesystems/Makefile
index 73d4650af1a5179f6d31926b0e1455b01353c5cb..85427d7f19b9b5dae3a7617a2e0d01182cbd19a9 100644 (file)
--- a/tools/testing/selftests/filesystems/Makefile
+++ b/tools/testing/selftests/filesystems/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
 CFLAGS += $(KHDR_INCLUDES)
-TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test
+TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test fclog
 TEST_GEN_PROGS_EXTENDED := dnotify_test
 
 include ../lib.mk

diff --git a/tools/testing/selftests/filesystems/fclog.c b/tools/testing/selftests/filesystems/fclog.c
new file mode 100644 (file)
index 0000000..912a8b7
--- /dev/null
+++ b/tools/testing/selftests/filesystems/fclog.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Author: Aleksa Sarai <cyphar@cyphar.com>
+ * Copyright (C) 2025 SUSE LLC.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mount.h>
+
+#include "../kselftest_harness.h"
+
+#define ASSERT_ERRNO(expected, _t, seen)                               \
+       __EXPECT(expected, #expected,                                   \
+               ({__typeof__(seen) _tmp_seen = (seen);                  \
+                 _tmp_seen >= 0 ? _tmp_seen : -errno; }), #seen, _t, 1)
+
+#define ASSERT_ERRNO_EQ(expected, seen) \
+       ASSERT_ERRNO(expected, ==, seen)
+
+#define ASSERT_SUCCESS(seen) \
+       ASSERT_ERRNO(0, <=, seen)
+
+FIXTURE(ns)
+{
+       int host_mntns;
+};
+
+FIXTURE_SETUP(ns)
+{
+       /* Stash the old mntns. */
+       self->host_mntns = open("/proc/self/ns/mnt", O_RDONLY|O_CLOEXEC);
+       ASSERT_SUCCESS(self->host_mntns);
+
+       /* Create a new mount namespace and make it private. */
+       ASSERT_SUCCESS(unshare(CLONE_NEWNS));
+       ASSERT_SUCCESS(mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL));
+}
+
+FIXTURE_TEARDOWN(ns)
+{
+       ASSERT_SUCCESS(setns(self->host_mntns, CLONE_NEWNS));
+       ASSERT_SUCCESS(close(self->host_mntns));
+}
+
+TEST_F(ns, fscontext_log_enodata)
+{
+       int fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC);
+       ASSERT_SUCCESS(fsfd);
+
+       /* A brand new fscontext has no log entries. */
+       char buf[128] = {};
+       for (int i = 0; i < 16; i++)
+               ASSERT_ERRNO_EQ(-ENODATA, read(fsfd, buf, sizeof(buf)));
+
+       ASSERT_SUCCESS(close(fsfd));
+}
+
+TEST_F(ns, fscontext_log_errorfc)
+{
+       int fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC);
+       ASSERT_SUCCESS(fsfd);
+
+       ASSERT_ERRNO_EQ(-EINVAL, fsconfig(fsfd, FSCONFIG_SET_STRING, "invalid-arg", "123", 0));
+
+       char buf[128] = {};
+       ASSERT_SUCCESS(read(fsfd, buf, sizeof(buf)));
+       EXPECT_STREQ("e tmpfs: Unknown parameter 'invalid-arg'\n", buf);
+
+       /* The message has been consumed. */
+       ASSERT_ERRNO_EQ(-ENODATA, read(fsfd, buf, sizeof(buf)));
+       ASSERT_SUCCESS(close(fsfd));
+}
+
+TEST_F(ns, fscontext_log_errorfc_after_fsmount)
+{
+       int fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC);
+       ASSERT_SUCCESS(fsfd);
+
+       ASSERT_ERRNO_EQ(-EINVAL, fsconfig(fsfd, FSCONFIG_SET_STRING, "invalid-arg", "123", 0));
+
+       ASSERT_SUCCESS(fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0));
+       int mfd = fsmount(fsfd, FSMOUNT_CLOEXEC, MOUNT_ATTR_NOEXEC | MOUNT_ATTR_NOSUID);
+       ASSERT_SUCCESS(mfd);
+       ASSERT_SUCCESS(move_mount(mfd, "", AT_FDCWD, "/tmp", MOVE_MOUNT_F_EMPTY_PATH));
+
+       /*
+        * The fscontext log should still contain data even after
+        * FSCONFIG_CMD_CREATE and fsmount().
+        */
+       char buf[128] = {};
+       ASSERT_SUCCESS(read(fsfd, buf, sizeof(buf)));
+       EXPECT_STREQ("e tmpfs: Unknown parameter 'invalid-arg'\n", buf);
+
+       /* The message has been consumed. */
+       ASSERT_ERRNO_EQ(-ENODATA, read(fsfd, buf, sizeof(buf)));
+       ASSERT_SUCCESS(close(fsfd));
+}
+
+TEST_F(ns, fscontext_log_emsgsize)
+{
+       int fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC);
+       ASSERT_SUCCESS(fsfd);
+
+       ASSERT_ERRNO_EQ(-EINVAL, fsconfig(fsfd, FSCONFIG_SET_STRING, "invalid-arg", "123", 0));
+
+       char buf[128] = {};
+       /*
+        * Attempting to read a message with too small a buffer should not
+        * result in the message getting consumed.
+        */
+       ASSERT_ERRNO_EQ(-EMSGSIZE, read(fsfd, buf, 0));
+       ASSERT_ERRNO_EQ(-EMSGSIZE, read(fsfd, buf, 1));
+       for (int i = 0; i < 16; i++)
+               ASSERT_ERRNO_EQ(-EMSGSIZE, read(fsfd, buf, 16));
+
+       ASSERT_SUCCESS(read(fsfd, buf, sizeof(buf)));
+       EXPECT_STREQ("e tmpfs: Unknown parameter 'invalid-arg'\n", buf);
+
+       /* The message has been consumed. */
+       ASSERT_ERRNO_EQ(-ENODATA, read(fsfd, buf, sizeof(buf)));
+       ASSERT_SUCCESS(close(fsfd));
+}
+
+TEST_HARNESS_MAIN