[LTP] [PATCH v3 ltp] Add Intel umip(User Mode Instruction Prevention) basic function tests
Cyril Hrubis
chrubis@suse.cz
Thu Nov 29 17:14:50 CET 2018
Hi!
> umip is a security feature present in new Intel Processors.
> Intel CPU like ICE lake or newer is required.
> When umip enabled, it prevents the execution of certain instructions
> and situation as below:
> when Current Privilege Level (CPL) is greater than 0, user space
> applications could not access to system-wide settings such as
> the global and local descriptor tables, the segment selectors to
> the current task state and the local descriptor table.
> umip is enabled by default at boot.
> umip will protect below instructions in user mode:
> * SGDT - Store Global Descriptor Table
> * SIDT - Store Interrupt Descriptor Table
> * SLDT - Store Local Descriptor Table
> * SMSW - Store Machine Status Word
> * STR - Store Task Register
> If CPU not support umip, you still could comment cpuinfo check code
> to verify anyway.
>
> Signed-off-by: Pengfei Xu <pengfei.xu@intel.com>
> ---
> runtest/secure_umip | 2 +
> testcases/kernel/security/umip/Makefile | 7 +
> testcases/kernel/security/umip/umip_gp_test.c | 203 ++++++++++++++++++++++++++
> 3 files changed, 212 insertions(+)
> create mode 100644 runtest/secure_umip
> create mode 100644 testcases/kernel/security/umip/Makefile
> create mode 100644 testcases/kernel/security/umip/umip_gp_test.c
>
> diff --git a/runtest/secure_umip b/runtest/secure_umip
> new file mode 100644
> index 000000000..4082bc2a3
> --- /dev/null
> +++ b/runtest/secure_umip
> @@ -0,0 +1,2 @@
> +#DESCRIPTION: CPU security feature UMIP test
> +umip_instruction_test umip_gp_test
> diff --git a/testcases/kernel/security/umip/Makefile b/testcases/kernel/security/umip/Makefile
> new file mode 100644
> index 000000000..18896b6f2
> --- /dev/null
> +++ b/testcases/kernel/security/umip/Makefile
> @@ -0,0 +1,7 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +
> +top_srcdir ?= ../../../..
> +
> +include $(top_srcdir)/include/mk/testcases.mk
> +
> +include $(top_srcdir)/include/mk/generic_leaf_target.mk
> diff --git a/testcases/kernel/security/umip/umip_gp_test.c b/testcases/kernel/security/umip/umip_gp_test.c
> new file mode 100644
> index 000000000..12a6d9c53
> --- /dev/null
> +++ b/testcases/kernel/security/umip/umip_gp_test.c
> @@ -0,0 +1,203 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +/*
> + * testcases/security/umip/umip_gp_test.c
> + * Copyright (C) 2018 Intel Corporation
> + * Author: Neri, Ricardo <ricardo.neri@intel.com>
> + * Pengfei, Xu <pengfei.xu@intel.com>
> + */
> +
> +/*
> + * This test will check if Intel umip(User-Mode Execution Prevention) is
> + * working.
> + *
> + * Intel CPU of ICE lake or newer is required for the test
> + * kconfig requirement:CONFIG_X86_INTEL_UMIP=y
> + *
> + */
> +
> +#define _GNU_SOURCE
> +#include <unistd.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/wait.h>
> +#include <signal.h>
> +
> +#include "tst_test.h"
> +
> +#define CPUINFO_FILE "/proc/cpuinfo"
> +
> +#define GDT_LEN 10
> +#define IDT_LEN 10
> +#define EXIT_VALUE 200
> +
> +static int fd = -1, sigsegv_cnt;
> +
> +static struct tcase {
> + enum {
> + sgdt,
> + sidt,
> + sldt,
> + smsw,
> + str
> + } option;
> + int exp_sig;
> +} tcases[] = {
> + {sgdt, SIGSEGV},
> + {sidt, SIGSEGV},
> + {sldt, SIGSEGV},
> + {smsw, SIGSEGV},
> + {str, SIGSEGV},
> +};
> +
> +static void asm_sgdt(void)
> +{
> + unsigned char val[GDT_LEN];
> +
> + memset(val, 0, sizeof(val));
> + tst_res(TINFO, "TEST sgdt, sgdt result save at [%p]", val);
> + asm volatile("sgdt %0\n" : "=m" (val));
> + tst_res(TINFO, "Test sgdt instruction finished");
> +}
> +
> +static void asm_sidt(void)
> +{
> + unsigned char val[IDT_LEN];
> +
> + memset(val, 0, sizeof(val));
> + tst_res(TINFO, "TEST sidt, sidt result save at [%p]\n", val);
> + asm volatile("sidt %0\n" : "=m" (val));
> + tst_res(TINFO, "Test sidt instruction finished");
> +}
> +
> +static void asm_sldt(void)
> +{
> + unsigned long val;
> +
> + tst_res(TINFO, "TEST sldt, sldt result save at [%p]\n", &val);
> + asm volatile("sldt %0\n" : "=m" (val));
> + tst_res(TINFO, "Test sldt instruction finished");
> +}
> +
> +static void asm_smsw(void)
> +{
> + unsigned long val;
> +
> + tst_res(TINFO, "TEST smsw, smsw result save at [%p]\n", &val);
> + asm volatile("smsw %0\n" : "=m" (val));
> + tst_res(TINFO, "Test sidt instruction finished");
> +}
> +
> +static void asm_str(void)
> +{
> + unsigned long val;
> +
> + tst_res(TINFO, "TEST str, str result save at [%p]\n", &val);
> + asm volatile("str %0\n" : "=m" (val));
> + tst_res(TINFO, "Test str instruction finished");
> +}
> +
> +static void verify_umip_instruction(unsigned int n)
> +{
> + int es = -1, status;
> + pid_t pid;
> + struct tcase *tc = &tcases[n];
> +
> + pid = SAFE_FORK();
> + if (pid == 0) {
> + switch (tc->option) {
> + case 0:
> + asm_sgdt();
> + break;
> + case 1:
> + asm_sidt();
> + break;
> + case 2:
> + asm_sldt();
> + break;
> + case 3:
> + asm_smsw();
> + break;
> + case 4:
> + asm_str();
> + break;
> + default:
> + tst_brk(TCONF, "Invalid tcase parameter:%d",
> + tc->option);
> + }
> + } else {
> + sleep(1);
NACK to sleep(1) in tests, you are supposed to use proper parent-child
synchronization.
What is the exact problem here?
> + SAFE_KILL(pid, SIGINT);
> + }
> +
> + SAFE_WAITPID(pid, &status, 0);
> +
> + if (WIFEXITED(status)) {
> + es = WEXITSTATUS(status);
> + tst_res(TPASS, "Child pid stopped as expected status:%d",
> + status);
> + } else
> + tst_res(TFAIL, "Could not get pid return value");
> + if (es == EXIT_VALUE) {
> + tst_res(TPASS, "Received expected return value %d", es);
> + } else {
> + tst_res(TWARN,
> + "Please confirm kconfig already set CONFIG_X86_INTEL_UMIP=y");
> + tst_res(TFAIL,
> + "Didn't receive SIGSEGV #11, return %d, expect:%d",
> + es, EXIT_VALUE);
> + }
> +}
> +
> +static void sig_handler(int signal)
> +{
> + int exp_sigsegv = 11;
> +
> + if (exp_sigsegv == signal) {
> + sigsegv_cnt++;
> + tst_res(TPASS, "Received SIGSEGV signal:%d, num:%d",
> + signal, sigsegv_cnt);
> + // signal handler by app, kernel will not kill, need exit
> + exit(EXIT_VALUE);
> + } else {
> + tst_res(TWARN, "Received unexpected signal:%d", signal);
> + }
Doing anything else than _exit() and a few async-signal-safe functions
in signal handler potentilly invokes undefined behavior and I've seen
deadlocks on standard output streams because of that. So NACK to this,
the safest option is to let the kernel kill the child and check that it
has been killed in the parent.
> +}
> +
> +static void setup(void)
> +{
> + int max = 2048, find = 0;
> + char buf[max];
> +
> + // cpuinfo should contain umip
> + fd = SAFE_OPEN(CPUINFO_FILE, O_RDONLY);
> + if (read(fd, buf, max) < 0)
> + tst_brk(TCONF, "read /proc/cpuinfo failed");
> + else if (strstr(buf, "umip")) {
> + tst_res(TINFO, "cpuinfo contain umip, cpu support umip");
> + find = 1;
> + }
> + if (find == 0)
> + tst_brk(TCONF,
> + "cpuinfo does not contain umip, not support umip");
> + SAFE_CLOSE(fd);
This would be much safer by reading lines with fgets() in a loop from a
FILE stream.
As you are reading a piece of /proc/cpuinfo here there is no guarantee
that the string is null terminated and this will likely crash on system
with many CPUs and no umip support.
> + SAFE_SIGNAL(SIGSEGV, sig_handler);
> +}
> +
> +static void cleanup(void)
> +{
> + if (fd != -1)
> + SAFE_CLOSE(fd);
> +}
> +
> +static struct tst_test test = {
> + .min_kver = "4.1",
> + .setup = setup,
> + .tcnt = ARRAY_SIZE(tcases),
> + .forks_child = 1,
> + .test = verify_umip_instruction,
> + .cleanup = cleanup,
> + .needs_root = 1,
> +};
> --
> 2.14.1
>
--
Cyril Hrubis
chrubis@suse.cz
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