[LTP] [PATCH] Add ltp pivot_root test

[Paul Lawrence]

Signed-off-by: Paul Lawrence <paullawrence@google.com>
---
 runtest/syscalls                              |   2 +
 testcases/kernel/syscalls/pivot_root/Makefile |  11 +
 .../kernel/syscalls/pivot_root/pivot_root01.c | 193 ++++++++++++++++++
 3 files changed, 206 insertions(+)
 create mode 100644 testcases/kernel/syscalls/pivot_root/Makefile
 create mode 100644 testcases/kernel/syscalls/pivot_root/pivot_root01.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 668c87cd1..debda74b8 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -835,6 +835,8 @@ pipe11 pipe11
 pipe2_01 pipe2_01
 pipe2_02 pipe2_02
 
+pivot_root01 pivot_root01
+
 poll01 poll01
 poll02 poll02
 
diff --git a/testcases/kernel/syscalls/pivot_root/Makefile b/testcases/kernel/syscalls/pivot_root/Makefile
new file mode 100644
index 000000000..6a3810270
--- /dev/null
+++ b/testcases/kernel/syscalls/pivot_root/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (c) 2019 Google, Inc.
+
+top_srcdir		?= ../../../..
+
+include $(top_srcdir)/include/mk/testcases.mk
+
+LDLIBS += $(CAP_LIBS)
+
+include $(top_srcdir)/include/mk/generic_leaf_target.mk
diff --git a/testcases/kernel/syscalls/pivot_root/pivot_root01.c b/testcases/kernel/syscalls/pivot_root/pivot_root01.c
new file mode 100644
index 000000000..d5f2bd1ca
--- /dev/null
+++ b/testcases/kernel/syscalls/pivot_root/pivot_root01.c
@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+//
+// Copyright (c) 2019 Google, Inc.
+
+#define _GNU_SOURCE
+
+#include "config.h"
+
+#include <errno.h>
+#include <lapi/syscalls.h>
+#include <sched.h>
+
+#include <sys/mount.h>
+#include <stdlib.h>
+
+#include "tst_test.h"
+
+#ifdef HAVE_UNSHARE
+
+#ifdef HAVE_LIBCAP
+#include <sys/capability.h>
+#endif
+
+#define CHROOT_DIR	"chroot"
+#define NEW_ROOT	"/new_root"
+#define PUT_OLD		"/new_root/put_old"
+#define PUT_OLD_FS	"/put_old_fs"
+#define PUT_OLD_BAD	"/put_old_fs/put_old"
+
+enum {
+	/*
+	 * Test consists of a series of steps that allow pivot_root to succeed,
+	 * which is run when param is NORMAL. All other values tweak one of the
+	 * steps to induce a failure, and check the errno is as expected.
+	 */
+	NORMAL,
+
+	/*
+	 * EBUSY
+	 * new_root or put_old are on the current root file system
+	 */
+	NEW_ROOT_ON_CURRENT_ROOT,
+
+	/*
+	 * EINVAL
+	 * put_old is not underneath new_root
+	 * Note: if put_old and new_root are on the same fs,
+	 * pivot_root fails with EBUSY before testing reachability
+	 */
+	PUT_OLD_NOT_UNDERNEATH_NEW_ROOT,
+
+	/*
+	 * ENOTDIR
+	 * new_root or put_old is not a directory
+	 */
+	PUT_OLD_NOT_DIR,
+
+	/*
+	 * EPERM
+	 * The calling process does not have the CAP_SYS_ADMIN capability.
+	 */
+	NO_CAP_SYS_ADMIN,
+};
+
+static const struct test_case {
+	int test_case;
+	int expected_error;
+} test_cases[] = {
+	{NORMAL, 0},
+	{NEW_ROOT_ON_CURRENT_ROOT, EBUSY},
+	{PUT_OLD_NOT_UNDERNEATH_NEW_ROOT, EINVAL},
+	{PUT_OLD_NOT_DIR, ENOTDIR},
+	{NO_CAP_SYS_ADMIN, EPERM},
+};
+
+#ifdef HAVE_LIBCAP
+static void drop_cap_sys_admin(void)
+{
+	cap_value_t cap_value[] = { CAP_SYS_ADMIN };
+	cap_t cap = cap_get_proc();
+	if (!cap)
+		tst_brk(TFAIL | TERRNO, "cap_get_proc failed");
+
+	if (cap_set_flag(cap, CAP_EFFECTIVE, 1, cap_value, CAP_CLEAR))
+		tst_brk(TFAIL | TERRNO, "cap_set_flag failed");
+
+	if (cap_set_proc(cap))
+		tst_brk(TFAIL | TERRNO, "cap_set_proc failed");
+}
+#endif
+
+static void run(unsigned int test_case)
+{
+	/* Work in child process - needed to undo unshare and chroot */
+	if (SAFE_FORK()) {
+		tst_reap_children();
+		return;
+	}
+
+	/* pivot_root requires no shared mounts exist in process namespace */
+	TEST(unshare(CLONE_NEWNS | CLONE_FS));
+	if (TST_RET == -1)
+		tst_brk(TFAIL | TERRNO, "unshare failed");
+
+	/*
+	 * Create an initial root dir. pivot_root doesn't work if the initial root
+	 * dir is a initramfs, so use chroot to create a safe environment
+	 */
+	SAFE_MOUNT("none", "/", NULL, MS_REC|MS_PRIVATE, NULL);
+	SAFE_MOUNT("none", CHROOT_DIR, "tmpfs", 0, 0);
+	SAFE_CHROOT(CHROOT_DIR);
+
+	SAFE_MKDIR(NEW_ROOT, 0777);
+
+	/*
+	 * pivot_root only works if new_root is a mount point, so mount a tmpfs
+	 * unless testing for that fail mode
+	 */
+	if (test_cases[test_case].test_case != NEW_ROOT_ON_CURRENT_ROOT)
+		SAFE_MOUNT("none", NEW_ROOT, "tmpfs", 0, 0);
+
+	/*
+	 * Create put_old under new_root, unless testing for that specific fail
+	 * mode
+	 */
+	const char* actual_put_old = NULL;
+	if (test_cases[test_case].test_case == PUT_OLD_NOT_UNDERNEATH_NEW_ROOT) {
+		actual_put_old = PUT_OLD_BAD;
+		SAFE_MKDIR(PUT_OLD_FS, 0777);
+		SAFE_MOUNT("none", PUT_OLD_FS, "tmpfs", 0, 0);
+		SAFE_MKDIR(PUT_OLD_BAD, 0777);
+	} else {
+		actual_put_old = PUT_OLD;
+
+		if (test_cases[test_case].test_case == PUT_OLD_NOT_DIR)
+			SAFE_CREAT(PUT_OLD, 0777);
+		else
+			SAFE_MKDIR(PUT_OLD, 0777);
+	}
+
+	if (test_cases[test_case].test_case == NO_CAP_SYS_ADMIN) {
+#ifdef HAVE_LIBCAP
+		drop_cap_sys_admin();
+#else
+		tst_res(TCONF,
+			"System doesn't have POSIX capabilities support");
+		return;
+#endif
+	}
+
+	TEST(syscall(__NR_pivot_root, NEW_ROOT, actual_put_old));
+
+	if (test_cases[test_case].test_case == NORMAL) {
+		if (TST_RET) {
+			tst_res(TFAIL | TERRNO, "pivot_root failed");
+			return;
+		} else {
+			tst_res(TPASS, "pivot_root succeeded");
+			return;
+		}
+	}
+
+	if (TST_RET == 0) {
+		tst_res(TFAIL, "pivot_root succeeded unexpectedly");
+		return;
+	}
+
+	if (errno != test_cases[test_case].expected_error) {
+		tst_res(TFAIL | TERRNO,	"pivot_root failed with wrong errno");
+		return;
+	}
+
+	tst_res(TPASS, "pivot_root failed as expected with %s",
+		strerror(errno));
+}
+
+static void setup(void)
+{
+	SAFE_MKDIR(CHROOT_DIR, 0777);
+}
+
+static struct tst_test test = {
+	.test = run,
+	.tcnt = ARRAY_SIZE(test_cases),
+	.needs_tmpdir = 1,
+	.needs_root = 1,
+	.forks_child = 1,
+	.setup = setup,
+};
+
+#else
+	TST_TEST_TCONF("unshare is undefined.");
+#endif
-- 
2.21.0.225.g810b269d1ac-goog