Commit 179ef035 authored by Gabriel Krisman Bertazi's avatar Gabriel Krisman Bertazi Committed by Thomas Gleixner
Browse files

selftests: Add kselftest for syscall user dispatch 



Implement functionality tests for syscall user dispatch.  In order to
make the test portable, refrain from open coding syscall dispatchers and
calculating glibc memory ranges.

Signed-off-by: default avatarGabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAndy Lutomirski <luto@kernel.org>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201127193238.821364-6-krisman@collabora.com
parent 11894468

tools/testing/selftests/Makefile

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@@ -56,6 +56,7 @@ TARGETS += sparc64 
TARGETS += splice

TARGETS += static_keys

TARGETS += sync

TARGETS += syscall_user_dispatch

TARGETS += sysctl

TARGETS += tc-testing

TARGETS += timens

tools/testing/selftests/syscall_user_dispatch/.gitignore

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# SPDX-License-Identifier: GPL-2.0-only

sud_test

sud_benchmark

tools/testing/selftests/syscall_user_dispatch/Makefile

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# SPDX-License-Identifier: GPL-2.0

top_srcdir = ../../../..

INSTALL_HDR_PATH = $(top_srcdir)/usr

LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/



CFLAGS += -Wall -I$(LINUX_HDR_PATH)



TEST_GEN_PROGS := sud_test

include ../lib.mk

tools/testing/selftests/syscall_user_dispatch/config

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CONFIG_GENERIC_ENTRY=y

tools/testing/selftests/syscall_user_dispatch/sud_test.c

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// SPDX-License-Identifier: GPL-2.0-only

/*

 * Copyright (c) 2020 Collabora Ltd.

 *

 * Test code for syscall user dispatch

 */



#define _GNU_SOURCE

#include <sys/prctl.h>

#include <sys/sysinfo.h>

#include <sys/syscall.h>

#include <signal.h>



#include <asm/unistd.h>

#include "../kselftest_harness.h"



#ifndef PR_SET_SYSCALL_USER_DISPATCH

# define PR_SET_SYSCALL_USER_DISPATCH	59

# define PR_SYS_DISPATCH_OFF	0

# define PR_SYS_DISPATCH_ON	1

#endif



#ifndef SYS_USER_DISPATCH

# define SYS_USER_DISPATCH	2

#endif



#ifdef __NR_syscalls

# define MAGIC_SYSCALL_1 (__NR_syscalls + 1) /* Bad Linux syscall number */

#else

# define MAGIC_SYSCALL_1 (0xff00)  /* Bad Linux syscall number */

#endif



#define SYSCALL_DISPATCH_ON(x) ((x) = 1)

#define SYSCALL_DISPATCH_OFF(x) ((x) = 0)



/* Test Summary:

 *

 * - dispatch_trigger_sigsys: Verify if PR_SET_SYSCALL_USER_DISPATCH is

 *   able to trigger SIGSYS on a syscall.

 *

 * - bad_selector: Test that a bad selector value triggers SIGSYS with

 *   si_errno EINVAL.

 *

 * - bad_prctl_param: Test that the API correctly rejects invalid

 *   parameters on prctl

 *

 * - dispatch_and_return: Test that a syscall is selectively dispatched

 *   to userspace depending on the value of selector.

 *

 * - disable_dispatch: Test that the PR_SYS_DISPATCH_OFF correctly

 *   disables the dispatcher

 *

 * - direct_dispatch_range: Test that a syscall within the allowed range

 *   can bypass the dispatcher.

 */



TEST_SIGNAL(dispatch_trigger_sigsys, SIGSYS)

{

	char sel = 0;

	struct sysinfo info;

	int ret;



	ret = sysinfo(&info);

	ASSERT_EQ(0, ret);



	ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);

	ASSERT_EQ(0, ret) {

		TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");

	}



	SYSCALL_DISPATCH_ON(sel);



	sysinfo(&info);



	EXPECT_FALSE(true) {

		TH_LOG("Unreachable!");

	}

}



TEST(bad_prctl_param)

{

	char sel = 0;

	int op;



	/* Invalid op */

	op = -1;

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0, 0, &sel);

	ASSERT_EQ(EINVAL, errno);



	/* PR_SYS_DISPATCH_OFF */

	op = PR_SYS_DISPATCH_OFF;



	/* offset != 0 */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, 0);

	EXPECT_EQ(EINVAL, errno);



	/* len != 0 */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0xff, 0);

	EXPECT_EQ(EINVAL, errno);



	/* sel != NULL */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, &sel);

	EXPECT_EQ(EINVAL, errno);



	/* Valid parameter */

	errno = 0;

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x0, 0x0);

	EXPECT_EQ(0, errno);



	/* PR_SYS_DISPATCH_ON */

	op = PR_SYS_DISPATCH_ON;



	/* Dispatcher region is bad (offset > 0 && len == 0) */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x1, 0x0, &sel);

	EXPECT_EQ(EINVAL, errno);

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, -1L, 0x0, &sel);

	EXPECT_EQ(EINVAL, errno);



	/* Invalid selector */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, op, 0x0, 0x1, (void *) -1);

	ASSERT_EQ(EFAULT, errno);



	/*

	 * Dispatcher range overflows unsigned long

	 */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 1, -1L, &sel);

	ASSERT_EQ(EINVAL, errno) {

		TH_LOG("Should reject bad syscall range");

	}



	/*

	 * Allowed range overflows usigned long

	 */

	prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, -1L, 0x1, &sel);

	ASSERT_EQ(EINVAL, errno) {

		TH_LOG("Should reject bad syscall range");

	}

}



/*

 * Use global selector for handle_sigsys tests, to avoid passing

 * selector to signal handler

 */

char glob_sel;

int nr_syscalls_emulated;

int si_code;

int si_errno;



static void handle_sigsys(int sig, siginfo_t *info, void *ucontext)

{

	si_code = info->si_code;

	si_errno = info->si_errno;



	if (info->si_syscall == MAGIC_SYSCALL_1)

		nr_syscalls_emulated++;



	/* In preparation for sigreturn. */

	SYSCALL_DISPATCH_OFF(glob_sel);

}



TEST(dispatch_and_return)

{

	long ret;

	struct sigaction act;

	sigset_t mask;



	glob_sel = 0;

	nr_syscalls_emulated = 0;

	si_code = 0;

	si_errno = 0;



	memset(&act, 0, sizeof(act));

	sigemptyset(&mask);



	act.sa_sigaction = handle_sigsys;

	act.sa_flags = SA_SIGINFO;

	act.sa_mask = mask;



	ret = sigaction(SIGSYS, &act, NULL);

	ASSERT_EQ(0, ret);



	/* Make sure selector is good prior to prctl. */

	SYSCALL_DISPATCH_OFF(glob_sel);



	ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &glob_sel);

	ASSERT_EQ(0, ret) {

		TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");

	}



	/* MAGIC_SYSCALL_1 doesn't exist. */

	SYSCALL_DISPATCH_OFF(glob_sel);

	ret = syscall(MAGIC_SYSCALL_1);

	EXPECT_EQ(-1, ret) {

		TH_LOG("Dispatch triggered unexpectedly");

	}



	/* MAGIC_SYSCALL_1 should be emulated. */

	nr_syscalls_emulated = 0;

	SYSCALL_DISPATCH_ON(glob_sel);



	ret = syscall(MAGIC_SYSCALL_1);

	EXPECT_EQ(MAGIC_SYSCALL_1, ret) {

		TH_LOG("Failed to intercept syscall");

	}

	EXPECT_EQ(1, nr_syscalls_emulated) {

		TH_LOG("Failed to emulate syscall");

	}

	ASSERT_EQ(SYS_USER_DISPATCH, si_code) {

		TH_LOG("Bad si_code in SIGSYS");

	}

	ASSERT_EQ(0, si_errno) {

		TH_LOG("Bad si_errno in SIGSYS");

	}

}



TEST_SIGNAL(bad_selector, SIGSYS)

{

	long ret;

	struct sigaction act;

	sigset_t mask;

	struct sysinfo info;



	glob_sel = 0;

	nr_syscalls_emulated = 0;

	si_code = 0;

	si_errno = 0;



	memset(&act, 0, sizeof(act));

	sigemptyset(&mask);



	act.sa_sigaction = handle_sigsys;

	act.sa_flags = SA_SIGINFO;

	act.sa_mask = mask;



	ret = sigaction(SIGSYS, &act, NULL);

	ASSERT_EQ(0, ret);



	/* Make sure selector is good prior to prctl. */

	SYSCALL_DISPATCH_OFF(glob_sel);



	ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &glob_sel);

	ASSERT_EQ(0, ret) {

		TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");

	}



	glob_sel = -1;



	sysinfo(&info);



	/* Even though it is ready to catch SIGSYS, the signal is

	 * supposed to be uncatchable.

	 */



	EXPECT_FALSE(true) {

		TH_LOG("Unreachable!");

	}

}



TEST(disable_dispatch)

{

	int ret;

	struct sysinfo info;

	char sel = 0;



	ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, 0, &sel);

	ASSERT_EQ(0, ret) {

		TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");

	}



	/* MAGIC_SYSCALL_1 doesn't exist. */

	SYSCALL_DISPATCH_OFF(glob_sel);



	ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_OFF, 0, 0, 0);

	EXPECT_EQ(0, ret) {

		TH_LOG("Failed to unset syscall user dispatch");

	}



	/* Shouldn't have any effect... */

	SYSCALL_DISPATCH_ON(glob_sel);



	ret = syscall(__NR_sysinfo, &info);

	EXPECT_EQ(0, ret) {

		TH_LOG("Dispatch triggered unexpectedly");

	}

}



TEST(direct_dispatch_range)

{

	int ret = 0;

	struct sysinfo info;

	char sel = 0;



	/*

	 * Instead of calculating libc addresses; allow the entire

	 * memory map and lock the selector.

	 */

	ret = prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON, 0, -1L, &sel);

	ASSERT_EQ(0, ret) {

		TH_LOG("Kernel does not support CONFIG_SYSCALL_USER_DISPATCH");

	}



	SYSCALL_DISPATCH_ON(sel);



	ret = sysinfo(&info);

	ASSERT_EQ(0, ret) {

		TH_LOG("Dispatch triggered unexpectedly");

	}

}



TEST_HARNESS_MAIN

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