selftests: add clone3() CAP_CHECKPOINT_RESTORE test

This adds a test that changes its UID, uses capabilities to
get CAP_CHECKPOINT_RESTORE and uses clone3() with set_tid to
create a process with a given PID as non-root.

Signed-off-by: Adrian Reber <areber@redhat.com>
Link: https://lore.kernel.org/r/20200719100418.2112740-8-areber@redhat.com
[christian.brauner@ubuntu.com: use TH_LOG() instead of ksft_print_msg()]
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore
index a81085742d40c01ba0db282b7ca95716901cba6c..83c0f6246055d8191d9bccf61c50353c707147e8 100644 (file)
--- a/tools/testing/selftests/clone3/.gitignore
+++ b/tools/testing/selftests/clone3/.gitignore
@@ -2,3 +2,4 @@
 clone3
 clone3_clear_sighand
 clone3_set_tid
+clone3_cap_checkpoint_restore

diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
index cf976c732906d0657d2cdfc89900242cbb2a3ebb..ef7564cb7abeab298f0bb654ca356bb13631aea5 100644 (file)
--- a/tools/testing/selftests/clone3/Makefile
+++ b/tools/testing/selftests/clone3/Makefile
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 CFLAGS += -g -I../../../../usr/include/
+LDLIBS += -lcap
 
-TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid
+TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid \
+       clone3_cap_checkpoint_restore
 
 include ../lib.mk

diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
new file mode 100644 (file)
index 0000000..9562425
--- /dev/null
+++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Based on Christian Brauner's clone3() example.
+ * These tests are assuming to be running in the host's
+ * PID namespace.
+ */
+
+/* capabilities related code based on selftests/bpf/test_verifier.c */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <sys/capability.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sched.h>
+
+#include "../kselftest_harness.h"
+#include "clone3_selftests.h"
+
+#ifndef MAX_PID_NS_LEVEL
+#define MAX_PID_NS_LEVEL 32
+#endif
+
+static void child_exit(int ret)
+{
+       fflush(stdout);
+       fflush(stderr);
+       _exit(ret);
+}
+
+static int call_clone3_set_tid(struct __test_metadata *_metadata,
+                              pid_t *set_tid, size_t set_tid_size)
+{
+       int status;
+       pid_t pid = -1;
+
+       struct clone_args args = {
+               .exit_signal = SIGCHLD,
+               .set_tid = ptr_to_u64(set_tid),
+               .set_tid_size = set_tid_size,
+       };
+
+       pid = sys_clone3(&args, sizeof(struct clone_args));
+       if (pid < 0) {
+               TH_LOG("%s - Failed to create new process", strerror(errno));
+               return -errno;
+       }
+
+       if (pid == 0) {
+               int ret;
+               char tmp = 0;
+
+               TH_LOG("I am the child, my PID is %d (expected %d)", getpid(), set_tid[0]);
+
+               if (set_tid[0] != getpid())
+                       child_exit(EXIT_FAILURE);
+               child_exit(EXIT_SUCCESS);
+       }
+
+       TH_LOG("I am the parent (%d). My child's pid is %d", getpid(), pid);
+
+       if (waitpid(pid, &status, 0) < 0) {
+               TH_LOG("Child returned %s", strerror(errno));
+               return -errno;
+       }
+
+       if (!WIFEXITED(status))
+               return -1;
+
+       return WEXITSTATUS(status);
+}
+
+static int test_clone3_set_tid(struct __test_metadata *_metadata,
+                              pid_t *set_tid, size_t set_tid_size)
+{
+       int ret;
+
+       TH_LOG("[%d] Trying clone3() with CLONE_SET_TID to %d", getpid(), set_tid[0]);
+       ret = call_clone3_set_tid(_metadata, set_tid, set_tid_size);
+       TH_LOG("[%d] clone3() with CLONE_SET_TID %d says:%d", getpid(), set_tid[0], ret);
+       return ret;
+}
+
+struct libcap {
+       struct __user_cap_header_struct hdr;
+       struct __user_cap_data_struct data[2];
+};
+
+static int set_capability(void)
+{
+       cap_value_t cap_values[] = { CAP_SETUID, CAP_SETGID };
+       struct libcap *cap;
+       int ret = -1;
+       cap_t caps;
+
+       caps = cap_get_proc();
+       if (!caps) {
+               perror("cap_get_proc");
+               return -1;
+       }
+
+       /* Drop all capabilities */
+       if (cap_clear(caps)) {
+               perror("cap_clear");
+               goto out;
+       }
+
+       cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET);
+       cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET);
+
+       cap = (struct libcap *) caps;
+
+       /* 40 -> CAP_CHECKPOINT_RESTORE */
+       cap->data[1].effective |= 1 << (40 - 32);
+       cap->data[1].permitted |= 1 << (40 - 32);
+
+       if (cap_set_proc(caps)) {
+               perror("cap_set_proc");
+               goto out;
+       }
+       ret = 0;
+out:
+       if (cap_free(caps))
+               perror("cap_free");
+       return ret;
+}
+
+TEST(clone3_cap_checkpoint_restore)
+{
+       pid_t pid;
+       int status;
+       int ret = 0;
+       pid_t set_tid[1];
+
+       test_clone3_supported();
+
+       EXPECT_EQ(getuid(), 0)
+               XFAIL(return, "Skipping all tests as non-root\n");
+
+       memset(&set_tid, 0, sizeof(set_tid));
+
+       /* Find the current active PID */
+       pid = fork();
+       if (pid == 0) {
+               TH_LOG("Child has PID %d", getpid());
+               child_exit(EXIT_SUCCESS);
+       }
+       ASSERT_GT(waitpid(pid, &status, 0), 0)
+               TH_LOG("Waiting for child %d failed", pid);
+
+       /* After the child has finished, its PID should be free. */
+       set_tid[0] = pid;
+
+       ASSERT_EQ(set_capability(), 0)
+               TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
+
+       ASSERT_EQ(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0), 0);
+
+       EXPECT_EQ(setgid(65534), 0)
+               TH_LOG("Failed to setgid(65534)");
+       ASSERT_EQ(setuid(65534), 0);
+
+       set_tid[0] = pid;
+       /* This would fail without CAP_CHECKPOINT_RESTORE */
+       ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), -EPERM);
+       ASSERT_EQ(set_capability(), 0)
+               TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
+       /* This should work as we have CAP_CHECKPOINT_RESTORE as non-root */
+       ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), 0);
+}
+
+TEST_HARNESS_MAIN