snd_seq01.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2018 SUSE LLC <nstange@suse.de>
 * Copyright (C) 2020 SUSE LLC <mdoucha@suse.cz>
 *
 * CVE-2018-7566
 *
 * Test for race condition when initializing client pool on /dev/snd/seq
 * Kernel crash fixed in:
 *
 *  commit d15d662e89fc667b90cd294b0eb45694e33144da
 *  Author: Takashi Iwai <tiwai@suse.de>
 *  Date:   Mon Feb 12 15:20:51 2018 +0100
 *
 *  ALSA: seq: Fix racy pool initializations
 */

#include <linux/types.h>
#include <time.h>
#include <sound/asound.h>
#include <sound/asequencer.h>

#include "tst_test.h"
#include "tst_fuzzy_sync.h"

static int fd = -1;
static int client_id;
static struct snd_seq_remove_events rminfo = {
	.remove_mode = SNDRV_SEQ_REMOVE_OUTPUT
};
static struct snd_seq_event ssev = {
	.flags = SNDRV_SEQ_TIME_STAMP_TICK | SNDRV_SEQ_TIME_MODE_REL,
	.queue = 0,
	.type = SNDRV_SEQ_EVENT_USR0,
	.time = { .tick = 10 }
};

static struct tst_fzsync_pair fzsync_pair;

static void reinit_pool(int pool_size)
{
	struct snd_seq_client_pool pconf = {
		.output_pool = pool_size,
		.client = client_id
	};

	ioctl(fd, SNDRV_SEQ_IOCTL_SET_CLIENT_POOL, &pconf);
}

static void race_ioctl(void)
{
	reinit_pool(512);
}

static void race_write(void)
{
	TEST(write(fd, &ssev, sizeof(ssev)));
}

void (*testfunc_list[])(void) = {race_ioctl, race_write};

static void setup(void)
{
	struct snd_seq_queue_info qconf = { .queue = 0 };

	errno = 0;
	fd = open("/dev/snd/seq", O_RDWR);

	if (fd == -1 && (errno == ENOENT || errno == EACCES))
		tst_brk(TCONF | TERRNO, "Cannot open /dev/snd/seq");

	if (fd < 0)
		tst_brk(TBROK | TERRNO, "Cannot open /dev/snd/seq");

	SAFE_IOCTL(fd, SNDRV_SEQ_IOCTL_CLIENT_ID, &client_id);
	SAFE_IOCTL(fd, SNDRV_SEQ_IOCTL_CREATE_QUEUE, &qconf);
	ssev.dest.client = client_id;

	fzsync_pair.exec_loops = 1000000;
	tst_fzsync_pair_init(&fzsync_pair);
}

static void cleanup(void)
{
	if (fd >= 0)
		SAFE_CLOSE(fd);
	tst_fzsync_pair_cleanup(&fzsync_pair);
}

static void *thread_run(void *arg)
{
	while (tst_fzsync_run_b(&fzsync_pair)) {
		tst_fzsync_start_race_b(&fzsync_pair);
		reinit_pool(10);
		tst_fzsync_end_race_b(&fzsync_pair);
	}

	return arg;
}

static void run(unsigned int n)
{
	tst_fzsync_pair_reset(&fzsync_pair, thread_run);

	while (tst_fzsync_run_a(&fzsync_pair)) {
		reinit_pool(5);
		SAFE_IOCTL(fd, SNDRV_SEQ_IOCTL_REMOVE_EVENTS, &rminfo);
		tst_fzsync_start_race_a(&fzsync_pair);
		testfunc_list[n]();
		tst_fzsync_end_race_a(&fzsync_pair);

		if (tst_taint_check()) {
			tst_res(TFAIL, "Kernel is vulnerable");
			return;
		}
	}

	tst_res(TPASS, "Nothing bad happened, probably");
}

static struct tst_test test = {
	.test = run,
	.tcnt = ARRAY_SIZE(testfunc_list),
	.setup = setup,
	.cleanup = cleanup,
	.max_runtime = 60,
	.taint_check = TST_TAINT_W | TST_TAINT_D,
	.tags = (const struct tst_tag[]) {
		{"linux-git", "d15d662e89fc"},
		{"CVE", "2018-7566"},
		{}
	}
};