prctl - module autoload mode - v5

pr_modules_autoload_mode_test.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/prctl.h>

#include <sys/prctl.h>
#include <sys/ptrace.h>

enum {
	MODULES_AUTOLOAD_ALLOWED	= 0,
	MODULES_AUTOLOAD_PRIVILEGED	= 1,
	MODULES_AUTOLOAD_DISABLED	= 2,
};

#ifndef PR_SET_MODULES_AUTOLOAD_MODE
#define PR_SET_MODULES_AUTOLOAD_MODE	50
#define PR_GET_MODULES_AUTOLOAD_MODE	51
#endif

extern char **environ;
static char *args[] = { "/bin/bash", NULL };

int exec_command(int mode)
{
	int ret;

	ret = prctl(PR_SET_MODULES_AUTOLOAD_MODE, mode, 0, 0, 0);
	if (ret < 0) {
		fprintf(stderr, "Error PR_SET_MODULES_AUTOLOAD_MODE to 2 failed: %d (%m)\n", -errno);
		return EXIT_FAILURE;
	}

	ret = prctl(PR_GET_MODULES_AUTOLOAD_MODE, 0, 0, 0, 0);
	if (ret < 0) {
		fprintf(stderr, "Error PR_GET_MODULES_AUTOLOAD_MODE failed: %d (%m)\n", -errno);
		return EXIT_FAILURE;
	}

	printf("task modules_autoload_mode: %d\n", ret);
	execv(args[0], args);

	fprintf(stderr, "error on execve(): %d  (%m)\n", -errno);
	exit(EXIT_FAILURE);
}

int main(int argc, const char **argv)
{
	int ret;
	int mode = 0;

	if (argc > 1) {
		errno = 0;
		mode = strtol(argv[1], NULL, 10);
		if (errno != 0 && mode == 0) {
			fprintf(stderr, "Error parsing argument\n");
			return EXIT_FAILURE;
		}
	}

	if (mode > 0)
		return exec_command(mode);

	ret = prctl(PR_GET_MODULES_AUTOLOAD_MODE, 0, 0, 0, 0);
	if (ret < 0) {
		fprintf(stderr, "Error PR_GET_MODULES_AUTOLOAD_MODE failed: %d (%m)\n", -errno);
		return EXIT_FAILURE;
	}

	ret = prctl(PR_SET_MODULES_AUTOLOAD_MODE, MODULES_AUTOLOAD_PRIVILEGED,
		    0, 0, 0);
	if (ret < 0) {
		fprintf(stderr, "Error PR_SET_MODULES_AUTOLOAD_MODE to 1 failed: %d (%m)\n", -errno);
		return EXIT_FAILURE;
	}

	/* Pass extra non-zero argument */
	ret = prctl(PR_GET_MODULES_AUTOLOAD_MODE, 1, 0, 0, 0);
	if (ret >= 0 || errno != EINVAL) {
		printf("Error PR_GET_MODULES_AUTOLOAD_MODE should fail with -EINVAL");
		return EXIT_FAILURE;
	}

	ret = prctl(PR_GET_MODULES_AUTOLOAD_MODE, 0, 0, 0, 0);
	if (ret < 0) {
		fprintf(stderr, "Error PR_GET_MODULES_AUTOLOAD_MODE failed: %d (%m)\n", -errno);
		return EXIT_FAILURE;
	}

	printf("task modules_autoload_mode: %d\n", ret);
	if (ret != 1) {
		fprintf(stderr, "Error PR_GET_MODULES_AUTOLOAD_MODE should return 1\n");
		return EXIT_FAILURE;
	}

	/* Should fail with -EPERM */
	ret = prctl(PR_SET_MODULES_AUTOLOAD_MODE, MODULES_AUTOLOAD_ALLOWED,
		    0, 0, 0);
	if (ret < 0) {
		fprintf(stderr, "PR_SET_MODULES_AUTOLOAD_MODE to 0 failed: %d (%m)\n", -errno);
	} else {
		fprintf(stderr, "Error PR_SET_MODULES_AUTOLOAD_MODE to 0 succeeded\n");
		return EXIT_FAILURE;
	}

	return exec_command(MODULES_AUTOLOAD_DISABLED);
}