[LTP] [PATCH v2] Add ltp pivot_root test

[Paul Lawrence]

Replaced license
Merged all files into one parameterized file
Modified touse test_brk where appropriate

For the actual test results, using tst_brk from the child process
meant failures were not counted correctly, so I still use tst_res
and exit. Please let me know if there is a correct way of doing this.

Signed-off-by: Paul Lawrence <paullawrence@google.com>
---
 testcases/kernel/syscalls/pivot_root/Makefile |  11 ++
 .../kernel/syscalls/pivot_root/pivot_root01.c | 168 ++++++++++++++++++
 2 files changed, 179 insertions(+)
 create mode 100644 testcases/kernel/syscalls/pivot_root/Makefile
 create mode 100644 testcases/kernel/syscalls/pivot_root/pivot_root01.c

diff --git a/testcases/kernel/syscalls/pivot_root/Makefile b/testcases/kernel/syscalls/pivot_root/Makefile
new file mode 100644
index 000000000..ce8f8cb68
--- /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
+
+CFLAGS += -lcap
+
+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..3aa939ac9
--- /dev/null
+++ b/testcases/kernel/syscalls/pivot_root/pivot_root01.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+//
+// Copyright (c) 2019 Google, Inc.
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <linux/unistd.h>
+#include <sched.h>
+#include <sys/capability.h>
+#include <sys/mount.h>
+#include <stdlib.h>
+
+#include "tst_test.h"
+
+static const char* chroot_dir = "chroot";
+static const char* new_root = "/new_root";
+static const char* put_old = "/new_root/put_old";
+
+// 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.
+#define NORMAL 0
+
+// EBUSY
+// new_root or put_old are on the current root file system
+#define NEW_ROOT_ON_CURRENT_ROOT 1
+
+// 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
+#define PUT_OLD_NOT_UNDERNEATH_NEW_ROOT 2
+
+static const char* put_old_fs = "/put_old_fs";
+static const char* put_old_bad = "/put_old_fs/put_old";
+
+// ENOTDIR
+// new_root or put_old is not a directory
+#define PUT_OLD_NOT_DIR 3
+
+// EPERM
+// The calling process does not have the CAP_SYS_ADMIN capability.
+#define NO_CAP_SYS_ADMIN 4
+
+#define TEST_COUNT 5
+
+static int expected_error[] = {
+	0,
+	EBUSY,
+	EINVAL,
+	ENOTDIR,
+	EPERM,
+};
+
+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");
+}
+
+#ifdef HAVE_UNSHARE
+static void run(unsigned int param)
+{
+	// 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);
+
+	// Create our new root location
+	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 (param != 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 (param == 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;
+
+		// put_old must be a directory for success
+		if (param == PUT_OLD_NOT_DIR)
+			SAFE_CREAT(put_old, 0777);
+		else
+			SAFE_MKDIR(put_old, 0777);
+	}
+
+	if (param == NO_CAP_SYS_ADMIN)
+		drop_cap_sys_admin();
+
+	// Test the syscall
+	TEST(syscall(__NR_pivot_root, new_root, actual_put_old));
+
+	// If NORMAL it should have succeeded
+	if (param == NORMAL) {
+		if (TST_RET) {
+			tst_res(TFAIL | TERRNO, "pivot_root failed");
+			exit(TBROK);
+		} else {
+			tst_res(TPASS, "pivot_root succeeded");
+			exit(TPASS);
+		}
+	}
+
+	// pivot_root is expected to fail
+	if (TST_RET == 0) {
+		tst_res(TFAIL, "pivot_root succeeded unexpectedly");
+		exit(TBROK);
+	}
+
+	// Check error code is correct
+	if (errno != expected_error[param]) {
+		tst_res(TFAIL | TERRNO,	"pivot_root failed with wrong errno");
+		exit(TBROK);
+	}
+
+	tst_res(TPASS, "pivot_root failed as expected with %s",
+		strerror(errno));
+	exit(TPASS);
+}
+
+#else
+static void run(void)
+{
+	tst_brk(TCONF, NULL, "unshare is undefined.");
+}
+#endif
+
+static void setup(void)
+{
+	SAFE_MKDIR(chroot_dir, 0777);
+}
+
+static struct tst_test test = {
+	.test = run,
+	.tcnt = TEST_COUNT,
+	.needs_tmpdir = 1,
+	.needs_root = 1,
+	.forks_child = 1,
+	.setup = setup,
+};
-- 
2.21.0.352.gf09ad66450-goog