Re: [PATCH v2] selftests: add tests for clone3()

Christian Brauner
2019-11-06T15:59:22Z

On Mon, Nov 04, 2019 at 02:18:46PM +0100, Adrian Reber wrote:
> This adds tests for clone3() with different values and sizes
> of struct clone_args.
>
> This selftest was initially part of of the clone3() with PID selftest.
> After that patch was almost merged Eugene sent out a couple of patches
> to fix problems with these test.
>
> This commit now only contains the clone3() selftest after the LPC
> decision to rework clone3() with PID to allow setting the PID in
> multiple PID namespaces including all of Eugene's patches.
>
> Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
> Signed-off-by: Adrian Reber <areber@redhat.com>

Resending, since mutt messed-up the quoting due to a new configuration I
was testing.

A few more comments below.

Also, would you be open to adding tests here for the newly added .stack
and .stack_size API (cf. [1])?

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fa729c4df558936b4a1a7b3e2234011f44ede28b

> ---
> v2:
> - Applied Christian's suggestions
> - Skip root-only tests when running as non-root
> ---
> MAINTAINERS | 1 +
> tools/testing/selftests/Makefile | 1 +
> tools/testing/selftests/clone3/.gitignore | 1 +
> tools/testing/selftests/clone3/Makefile | 7 +
> tools/testing/selftests/clone3/clone3.c | 225 ++++++++++++++++++++++
> 5 files changed, 235 insertions(+)
> create mode 100644 tools/testing/selftests/clone3/.gitignore
> create mode 100644 tools/testing/selftests/clone3/Makefile
> create mode 100644 tools/testing/selftests/clone3/clone3.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cba1095547fd..0040b7a6410b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12829,6 +12829,7 @@ S: Maintained
> T: git git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git
> F: samples/pidfd/
> F: tools/testing/selftests/pidfd/
> +F: tools/testing/selftests/clone3/
> K: (?i)pidfd
> K: (?i)clone3
> K: \b(clone_args|kernel_clone_args)\b
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 4cdbae6f4e61..ad442364218a 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -4,6 +4,7 @@ TARGETS += bpf
> TARGETS += breakpoints
> TARGETS += capabilities
> TARGETS += cgroup
> +TARGETS += clone3
> TARGETS += cpufreq
> TARGETS += cpu-hotplug
> TARGETS += drivers/dma-buf
> diff --git a/tools/testing/selftests/clone3/.gitignore b/tools/testing/selftests/clone3/.gitignore
> new file mode 100644
> index 000000000000..85d9d3ba2524
> --- /dev/null
> +++ b/tools/testing/selftests/clone3/.gitignore
> @@ -0,0 +1 @@
> +clone3
> diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
> new file mode 100644
> index 000000000000..ea922c014ae4
> --- /dev/null
> +++ b/tools/testing/selftests/clone3/Makefile
> @@ -0,0 +1,7 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +CFLAGS += -I../../../../usr/include/
> +
> +TEST_GEN_PROGS := clone3
> +
> +include ../lib.mk
> diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c
> new file mode 100644
> index 000000000000..a982d95189bf
> --- /dev/null
> +++ b/tools/testing/selftests/clone3/clone3.c
> @@ -0,0 +1,225 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/* Based on Christian Brauner's clone3() example */
> +
> +#define _GNU_SOURCE
> +#include <errno.h>
> +#include <inttypes.h>
> +#include <linux/types.h>
> +#include <linux/sched.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.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.h"
> +
> +/*
> + * Different sizes of struct clone_args
> + */
> +#ifndef CLONE3_ARGS_SIZE_V0
> +#define CLONE3_ARGS_SIZE_V0 64
> +#endif
> +
> +enum test_mode {
> + CLONE3_ARGS_NO_TEST,
> + CLONE3_ARGS_ALL_0,
> + CLONE3_ARGS_ALL_1,
> + CLONE3_ARGS_INVAL_EXIT_SIGNAL_BIG,
> + CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG,
> + CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG,
> + CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG,
> +};
> +
> +static pid_t raw_clone(struct clone_args *args, size_t size)
> +{
> + return syscall(__NR_clone3, args, size);
> +}
> +
> +static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
> +{
> + struct clone_args args = {
> + .flags = flags,
> + .exit_signal = SIGCHLD,
> + };
> +
> + struct clone_args_extended {
> + struct clone_args args;
> + __aligned_u64 excess_space[2];
> + } args_ext;
> +
> + pid_t pid = -1;
> + int status;
> +
> + memset(&args_ext, 0, sizeof(args_ext));
> + if (size > sizeof(struct clone_args))
> + args_ext.excess_space[1] = 1;
> +
> + if (size == 0)
> + size = sizeof(struct clone_args);
> +
> + switch (test_mode) {
> + case CLONE3_ARGS_ALL_0:
> + args.flags = 0;
> + args.exit_signal = 0;
> + break;
> + case CLONE3_ARGS_ALL_1:

I don't fully understand this test case. What is this for exactly?

> + args.flags = 1;
> + args.pidfd = 1;
> + args.child_tid = 1;
> + args.parent_tid = 1;
> + args.exit_signal = 1;
> + args.stack = 1;
> + args. stack_size = 1;
> + args.tls = 1;
> + break;
> + case CLONE3_ARGS_INVAL_EXIT_SIGNAL_BIG:
> + args.exit_signal = 0xbadc0ded00000000ULL;
> + break;
> + case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG:
> + args.exit_signal = 0x0000000080000000ULL;
> + break;
> + case CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG:
> + args.exit_signal = 0x0000000000000100ULL;
> + break;
> + case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG:
> + args.exit_signal = 0x00000000000000f0ULL;
> + break;
> + }
> +
> + memcpy(&args_ext.args, &args, sizeof(struct clone_args));
> +
> + pid = raw_clone((struct clone_args *)&args_ext, size);
> + if (pid < 0) {
> + ksft_print_msg("%s - Failed to create new process\n",
> + strerror(errno));
> + return -errno;
> + }
> +
> + if (pid == 0) {
> + ksft_print_msg("I am the child, my PID is %d\n", getpid());
> + _exit(EXIT_SUCCESS);
> + }
> +
> + ksft_print_msg("I am the parent (%d). My child's pid is %d\n",
> + getpid(), pid);
> +
> + if (wait(&status) < 0) {
> + ksft_print_msg("Child returned %s\n", strerror(errno));
> + return -errno;
> + }
> + if (WEXITSTATUS(status))
> + return WEXITSTATUS(status);
> +
> + return 0;
> +}
> +
> +static void test_clone3(uint64_t flags, size_t size, int expected,
> + enum test_mode test_mode)
> +{
> + int ret;
> +
> + ksft_print_msg(
> + "[%d] Trying clone3() with flags %#" PRIx64 " (size %zu)\n",
> + getpid(), flags, size);
> + ret = call_clone3(flags, size, test_mode);
> + ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n",
> + getpid(), ret, expected);
> + if (ret != expected)
> + ksft_test_result_fail(
> + "[%d] Result (%d) is different than expected (%d)\n",
> + getpid(), ret, expected);
> + else
> + ksft_test_result_pass(
> + "[%d] Result (%d) matches expectation (%d)\n",
> + getpid(), ret, expected);
> +}
> +int main(int argc, char *argv[])
> +{
> + pid_t pid;
> +
> + uid_t uid = getuid();
> +
> + ksft_print_header();
> + ksft_set_plan(17);
> +
> + /* Just a simple clone3() should return 0.*/
> + test_clone3(0, 0, 0, CLONE3_ARGS_NO_TEST);
> +
> + /* Do a clone3() in a new PID NS.*/
> + if (uid == 0)
> + test_clone3(CLONE_NEWPID, 0, 0, CLONE3_ARGS_NO_TEST);
> + else
> + ksft_test_result_skip("Skipping clone3() with CLONE_NEWPID\n");
> +
> + /* Do a clone3() with CLONE3_ARGS_SIZE_V0. */
> + test_clone3(0, CLONE3_ARGS_SIZE_V0, 0, CLONE3_ARGS_NO_TEST);
> +
> + /* Do a clone3() with CLONE3_ARGS_SIZE_V0 - 8 */
> + test_clone3(0, CLONE3_ARGS_SIZE_V0 - 8, -EINVAL, CLONE3_ARGS_NO_TEST);
> +
> + /* Do a clone3() with sizeof(struct clone_args) + 8 */
> + test_clone3(0, sizeof(struct clone_args) + 8, 0, CLONE3_ARGS_NO_TEST);
> +
> + /* Do a clone3() with all members set to 1 */
> + test_clone3(0, 0, -EINVAL, CLONE3_ARGS_ALL_1);
> +
> + /* Do a clone3() with exit_signal having highest 32 bits non-zero */
> + test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_BIG);
> +
> + /* Do a clone3() with negative 32-bit exit_signal */
> + test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG);
> +
> + /* Do a clone3() with exit_signal not fitting into CSIGNAL mask */
> + test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG);
> +
> + /* Do a clone3() with NSIG < exit_signal < CSIG */
> + test_clone3(0, 0, -EINVAL, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG);
> +
> + /*
> + * Do a clone3() with sizeof(struct clone_args) + 8
> + * and all members set to 0. This resets exit_signal and wait()
> + * will not get a result.
> + */
> + test_clone3(0, sizeof(struct clone_args) + 8, -ECHILD,
> + CLONE3_ARGS_ALL_0);

Ah, I haven't caught this during the first review. No, that's not
correct. You don't get a signal since exit_signal is 0, that's correct
_but_ you still need to wait on the child. You don't see the child
because the kernel will by default not wait on clone()-children aka
processes created with exit_signal != SIGCHLD. To wait on
clone()-children as well, you need to set __WCLONE or __WALL in the
options argument for wait{p}id(2).

> +
> + /*
> + * Do a clone3() with sizeof(struct clone_args) + 8
> + * and all members set to 0.
> + */
> + test_clone3(0, sizeof(struct clone_args) + 8, -EINVAL,
> + CLONE3_ARGS_ALL_1);

The comment and the test don't line up. :)

> +
> + /* Do a clone3() with > page size */
> + test_clone3(0, getpagesize() + 8, -E2BIG, CLONE3_ARGS_NO_TEST);
> +
> + /* Do a clone3() with CLONE3_ARGS_SIZE_V0 in a new PID NS. */
> + if (uid == 0)
> + test_clone3(CLONE_NEWPID, CLONE3_ARGS_SIZE_V0, 0,
> + CLONE3_ARGS_NO_TEST);
> + else
> + ksft_test_result_skip("Skipping clone3() with CLONE_NEWPID\n");
> +
> + /* Do a clone3() with CLONE3_ARGS_SIZE_V0 - 8 in a new PID NS */
> + test_clone3(CLONE_NEWPID, CLONE3_ARGS_SIZE_V0 - 8, -EINVAL,
> + CLONE3_ARGS_NO_TEST);
> +
> + /* Do a clone3() with sizeof(struct clone_args) + 8 in a new PID NS */
> + if (uid == 0)
> + test_clone3(CLONE_NEWPID, sizeof(struct clone_args) + 8, 0,
> + CLONE3_ARGS_NO_TEST);
> + else
> + ksft_test_result_skip("Skipping clone3() with CLONE_NEWPID\n");
> +
> + /* Do a clone3() with > page size in a new PID NS */
> + test_clone3(CLONE_NEWPID, getpagesize() + 8, -E2BIG,
> + CLONE3_ARGS_NO_TEST);
> +
> + return !ksft_get_fail_cnt() ? ksft_exit_pass() : ksft_exit_fail();
> +}
> --
> 2.23.0
>