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Message-ID: <CAGXu5j+WTyiMarydzwHH_9aJ_DChLMcK+SRA_rWNBxnwP1z3VA@mail.gmail.com>
Date: Thu, 11 Jan 2018 20:12:18 -0800
From: Kees Cook <keescook@...omium.org>
To: Andy Lutomirski <luto@...nel.org>
Cc: X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Hugh Dickins <hughd@...gle.com>,
"# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH] selftests/x86: Add test_vsyscall
On Thu, Jan 11, 2018 at 5:16 PM, Andy Lutomirski <luto@...nel.org> wrote:
> This tests that the vsyscall entries do what they're expected to do.
> It also confirms that attempts to read the vsyscall page behave as
> expected.
>
> If changes are made to the vsyscall code or its memory map handling,
> running this test in all three of vsyscall=none, vsyscall=emulate,
> and vsyscall=native are helpful.
>
> (Because it's easy, this also compares the vsyscall results to their
> vDSO equivalents.)
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
Acked-by: Kees Cook <keescook@...omium.org>
Tested-by: Kees Cook <keescook@...omium.org>
(random note: if you're crazy and built with CONFIG_COMPAT_VDSO, this
doesn't actually fail, it just kind of limps along with warnings and
"RUN" but no "OK".)
-Kees
> ---
>
> Note to KAISER backporters: please test this under all three
> vsyscall modes. Also, in the emulate and native modes, make sure
> that test_vsyscall_64 agrees with the command line or config
> option as to which mode you're in. It's quite easy to mess up
> the kernel such that native mode accidentally emulates
> or vice versa.
>
> Greg, etc: please backport this to all your Meltdown-patched
> kernels. It'll help make sure the patches didn't regress
> vsyscalls.
>
> Changes from RFC version:
> - Doesn't warn on 32-bit
> - Detects native vs emulate
>
> tools/testing/selftests/x86/Makefile | 2 +-
> tools/testing/selftests/x86/test_vsyscall.c | 500 ++++++++++++++++++++++++++++
> 2 files changed, 501 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/x86/test_vsyscall.c
>
> diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
> index 939a337128db..5d4f10ac2af2 100644
> --- a/tools/testing/selftests/x86/Makefile
> +++ b/tools/testing/selftests/x86/Makefile
> @@ -7,7 +7,7 @@ include ../lib.mk
>
> TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
> check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test ioperm \
> - protection_keys test_vdso
> + protection_keys test_vdso test_vsyscall
> TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
> test_FCMOV test_FCOMI test_FISTTP \
> vdso_restorer
> diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
> new file mode 100644
> index 000000000000..7a744fa7b786
> --- /dev/null
> +++ b/tools/testing/selftests/x86/test_vsyscall.c
> @@ -0,0 +1,500 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#define _GNU_SOURCE
> +
> +#include <stdio.h>
> +#include <sys/time.h>
> +#include <time.h>
> +#include <stdlib.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +#include <dlfcn.h>
> +#include <string.h>
> +#include <inttypes.h>
> +#include <signal.h>
> +#include <sys/ucontext.h>
> +#include <errno.h>
> +#include <err.h>
> +#include <sched.h>
> +#include <stdbool.h>
> +#include <setjmp.h>
> +
> +#ifdef __x86_64__
> +# define VSYS(x) (x)
> +#else
> +# define VSYS(x) 0
> +#endif
> +
> +#ifndef SYS_getcpu
> +# ifdef __x86_64__
> +# define SYS_getcpu 309
> +# else
> +# define SYS_getcpu 318
> +# endif
> +#endif
> +
> +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
> + int flags)
> +{
> + struct sigaction sa;
> + memset(&sa, 0, sizeof(sa));
> + sa.sa_sigaction = handler;
> + sa.sa_flags = SA_SIGINFO | flags;
> + sigemptyset(&sa.sa_mask);
> + if (sigaction(sig, &sa, 0))
> + err(1, "sigaction");
> +}
> +
> +/* vsyscalls and vDSO */
> +bool should_read_vsyscall = false;
> +
> +typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
> +gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
> +gtod_t vdso_gtod;
> +
> +typedef int (*vgettime_t)(clockid_t, struct timespec *);
> +vgettime_t vdso_gettime;
> +
> +typedef long (*time_func_t)(time_t *t);
> +time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
> +time_func_t vdso_time;
> +
> +typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
> +getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
> +getcpu_t vdso_getcpu;
> +
> +static void init_vdso(void)
> +{
> + void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
> + if (!vdso)
> + vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
> + if (!vdso) {
> + printf("[WARN]\tfailed to find vDSO\n");
> + return;
> + }
> +
> + vdso_gtod = (gtod_t)dlsym(vdso, "__vdso_gettimeofday");
> + if (!vdso_gtod)
> + printf("[WARN]\tfailed to find gettimeofday in vDSO\n");
> +
> + vdso_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
> + if (!vdso_gettime)
> + printf("[WARN]\tfailed to find clock_gettime in vDSO\n");
> +
> + vdso_time = (time_func_t)dlsym(vdso, "__vdso_time");
> + if (!vdso_time)
> + printf("[WARN]\tfailed to find time in vDSO\n");
> +
> + vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
> + if (!vdso_getcpu) {
> + /* getcpu() was never wired up in the 32-bit vDSO. */
> + printf("[%s]\tfailed to find getcpu in vDSO\n",
> + sizeof(long) == 8 ? "WARN" : "NOTE");
> + }
> +}
> +
> +static int init_vsys(void)
> +{
> +#ifdef __x86_64__
> + int nerrs = 0;
> + FILE *maps;
> + char line[128];
> + bool found = false;
> +
> + maps = fopen("/proc/self/maps", "r");
> + if (!maps) {
> + printf("[WARN]\tCould not open /proc/self/maps -- assuming vsyscall is r-x\n");
> + should_read_vsyscall = true;
> + return 0;
> + }
> +
> + while (fgets(line, sizeof(line), maps)) {
> + char r, x;
> + void *start, *end;
> + char name[128];
> + if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
> + &start, &end, &r, &x, name) != 5)
> + continue;
> +
> + if (strcmp(name, "[vsyscall]"))
> + continue;
> +
> + printf("\tvsyscall map: %s", line);
> +
> + if (start != (void *)0xffffffffff600000 ||
> + end != (void *)0xffffffffff601000) {
> + printf("[FAIL]\taddress range is nonsense\n");
> + nerrs++;
> + }
> +
> + printf("\tvsyscall permissions are %c-%c\n", r, x);
> + should_read_vsyscall = (r == 'r');
> + if (x != 'x') {
> + vgtod = NULL;
> + vtime = NULL;
> + vgetcpu = NULL;
> + }
> +
> + found = true;
> + break;
> + }
> +
> + fclose(maps);
> +
> + if (!found) {
> + printf("\tno vsyscall map in /proc/self/maps\n");
> + should_read_vsyscall = false;
> + vgtod = NULL;
> + vtime = NULL;
> + vgetcpu = NULL;
> + }
> +
> + return nerrs;
> +#else
> + return 0;
> +#endif
> +}
> +
> +/* syscalls */
> +static inline long sys_gtod(struct timeval *tv, struct timezone *tz)
> +{
> + return syscall(SYS_gettimeofday, tv, tz);
> +}
> +
> +static inline int sys_clock_gettime(clockid_t id, struct timespec *ts)
> +{
> + return syscall(SYS_clock_gettime, id, ts);
> +}
> +
> +static inline long sys_time(time_t *t)
> +{
> + return syscall(SYS_time, t);
> +}
> +
> +static inline long sys_getcpu(unsigned * cpu, unsigned * node,
> + void* cache)
> +{
> + return syscall(SYS_getcpu, cpu, node, cache);
> +}
> +
> +static jmp_buf jmpbuf;
> +
> +static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
> +{
> + siglongjmp(jmpbuf, 1);
> +}
> +
> +static double tv_diff(const struct timeval *a, const struct timeval *b)
> +{
> + return (double)(a->tv_sec - b->tv_sec) +
> + (double)((int)a->tv_usec - (int)b->tv_usec) * 1e-6;
> +}
> +
> +static int check_gtod(const struct timeval *tv_sys1,
> + const struct timeval *tv_sys2,
> + const struct timezone *tz_sys,
> + const char *which,
> + const struct timeval *tv_other,
> + const struct timezone *tz_other)
> +{
> + int nerrs = 0;
> + double d1, d2;
> +
> + if (tz_other && (tz_sys->tz_minuteswest != tz_other->tz_minuteswest || tz_sys->tz_dsttime != tz_other->tz_dsttime)) {
> + printf("[FAIL] %s tz mismatch\n", which);
> + nerrs++;
> + }
> +
> + d1 = tv_diff(tv_other, tv_sys1);
> + d2 = tv_diff(tv_sys2, tv_other);
> + printf("\t%s time offsets: %lf %lf\n", which, d1, d2);
> +
> + if (d1 < 0 || d2 < 0) {
> + printf("[FAIL]\t%s time was inconsistent with the syscall\n", which);
> + nerrs++;
> + } else {
> + printf("[OK]\t%s gettimeofday()'s timeval was okay\n", which);
> + }
> +
> + return nerrs;
> +}
> +
> +static int test_gtod(void)
> +{
> + struct timeval tv_sys1, tv_sys2, tv_vdso, tv_vsys;
> + struct timezone tz_sys, tz_vdso, tz_vsys;
> + long ret_vdso = -1;
> + long ret_vsys = -1;
> + int nerrs = 0;
> +
> + printf("[RUN]\ttest gettimeofday()\n");
> +
> + if (sys_gtod(&tv_sys1, &tz_sys) != 0)
> + err(1, "syscall gettimeofday");
> + if (vdso_gtod)
> + ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso);
> + if (vgtod)
> + ret_vsys = vgtod(&tv_vsys, &tz_vsys);
> + if (sys_gtod(&tv_sys2, &tz_sys) != 0)
> + err(1, "syscall gettimeofday");
> +
> + if (vdso_gtod) {
> + if (ret_vdso == 0) {
> + nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vDSO", &tv_vdso, &tz_vdso);
> + } else {
> + printf("[FAIL]\tvDSO gettimeofday() failed: %ld\n", ret_vdso);
> + nerrs++;
> + }
> + }
> +
> + if (vgtod) {
> + if (ret_vsys == 0) {
> + nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys);
> + } else {
> + printf("[FAIL]\tvsys gettimeofday() failed: %ld\n", ret_vsys);
> + nerrs++;
> + }
> + }
> +
> + return nerrs;
> +}
> +
> +static int test_time(void) {
> + int nerrs = 0;
> +
> + printf("[RUN]\ttest time()\n");
> + long t_sys1, t_sys2, t_vdso = 0, t_vsys = 0;
> + long t2_sys1 = -1, t2_sys2 = -1, t2_vdso = -1, t2_vsys = -1;
> + t_sys1 = sys_time(&t2_sys1);
> + if (vdso_time)
> + t_vdso = vdso_time(&t2_vdso);
> + if (vtime)
> + t_vsys = vtime(&t2_vsys);
> + t_sys2 = sys_time(&t2_sys2);
> + if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) {
> + printf("[FAIL]\tsyscall failed (ret1:%ld output1:%ld ret2:%ld output2:%ld)\n", t_sys1, t2_sys1, t_sys2, t2_sys2);
> + nerrs++;
> + return nerrs;
> + }
> +
> + if (vdso_time) {
> + if (t_vdso < 0 || t_vdso != t2_vdso) {
> + printf("[FAIL]\tvDSO failed (ret:%ld output:%ld)\n", t_vdso, t2_vdso);
> + nerrs++;
> + } else if (t_vdso < t_sys1 || t_vdso > t_sys2) {
> + printf("[FAIL]\tvDSO returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vdso, t_sys2);
> + nerrs++;
> + } else {
> + printf("[OK]\tvDSO time() is okay\n");
> + }
> + }
> +
> + if (vtime) {
> + if (t_vsys < 0 || t_vsys != t2_vsys) {
> + printf("[FAIL]\tvsyscall failed (ret:%ld output:%ld)\n", t_vsys, t2_vsys);
> + nerrs++;
> + } else if (t_vsys < t_sys1 || t_vsys > t_sys2) {
> + printf("[FAIL]\tvsyscall returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vsys, t_sys2);
> + nerrs++;
> + } else {
> + printf("[OK]\tvsyscall time() is okay\n");
> + }
> + }
> +
> + return nerrs;
> +}
> +
> +static int test_getcpu(int cpu)
> +{
> + int nerrs = 0;
> + long ret_sys, ret_vdso = -1, ret_vsys = -1;
> +
> + printf("[RUN]\tgetcpu() on CPU %d\n", cpu);
> +
> + cpu_set_t cpuset;
> + CPU_ZERO(&cpuset);
> + CPU_SET(cpu, &cpuset);
> + if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
> + printf("[SKIP]\tfailed to force CPU %d\n", cpu);
> + return nerrs;
> + }
> +
> + unsigned cpu_sys, cpu_vdso, cpu_vsys, node_sys, node_vdso, node_vsys;
> + unsigned node = 0;
> + bool have_node = false;
> + ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
> + if (vdso_getcpu)
> + ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
> + if (vgetcpu)
> + ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
> +
> + if (ret_sys == 0) {
> + if (cpu_sys != cpu) {
> + printf("[FAIL]\tsyscall reported CPU %hu but should be %d\n", cpu_sys, cpu);
> + nerrs++;
> + }
> +
> + have_node = true;
> + node = node_sys;
> + }
> +
> + if (vdso_getcpu) {
> + if (ret_vdso) {
> + printf("[FAIL]\tvDSO getcpu() failed\n");
> + nerrs++;
> + } else {
> + if (!have_node) {
> + have_node = true;
> + node = node_vdso;
> + }
> +
> + if (cpu_vdso != cpu) {
> + printf("[FAIL]\tvDSO reported CPU %hu but should be %d\n", cpu_vdso, cpu);
> + nerrs++;
> + } else {
> + printf("[OK]\tvDSO reported correct CPU\n");
> + }
> +
> + if (node_vdso != node) {
> + printf("[FAIL]\tvDSO reported node %hu but should be %hu\n", node_vdso, node);
> + nerrs++;
> + } else {
> + printf("[OK]\tvDSO reported correct node\n");
> + }
> + }
> + }
> +
> + if (vgetcpu) {
> + if (ret_vsys) {
> + printf("[FAIL]\tvsyscall getcpu() failed\n");
> + nerrs++;
> + } else {
> + if (!have_node) {
> + have_node = true;
> + node = node_vsys;
> + }
> +
> + if (cpu_vsys != cpu) {
> + printf("[FAIL]\tvsyscall reported CPU %hu but should be %d\n", cpu_vsys, cpu);
> + nerrs++;
> + } else {
> + printf("[OK]\tvsyscall reported correct CPU\n");
> + }
> +
> + if (node_vsys != node) {
> + printf("[FAIL]\tvsyscall reported node %hu but should be %hu\n", node_vsys, node);
> + nerrs++;
> + } else {
> + printf("[OK]\tvsyscall reported correct node\n");
> + }
> + }
> + }
> +
> + return nerrs;
> +}
> +
> +static int test_vsys_r(void)
> +{
> +#ifdef __x86_64__
> + printf("[RUN]\tChecking read access to the vsyscall page\n");
> + bool can_read;
> + if (sigsetjmp(jmpbuf, 1) == 0) {
> + *(volatile int *)0xffffffffff600000;
> + can_read = true;
> + } else {
> + can_read = false;
> + }
> +
> + if (can_read && !should_read_vsyscall) {
> + printf("[FAIL]\tWe have read access, but we shouldn't\n");
> + return 1;
> + } else if (!can_read && should_read_vsyscall) {
> + printf("[FAIL]\tWe don't have read access, but we should\n");
> + return 1;
> + } else {
> + printf("[OK]\tgot expected result\n");
> + }
> +#endif
> +
> + return 0;
> +}
> +
> +
> +#ifdef __x86_64__
> +#define X86_EFLAGS_TF (1UL << 8)
> +static volatile sig_atomic_t num_vsyscall_traps;
> +
> +static unsigned long get_eflags(void)
> +{
> + unsigned long eflags;
> + asm volatile ("pushfq\n\tpopq %0" : "=rm" (eflags));
> + return eflags;
> +}
> +
> +static void set_eflags(unsigned long eflags)
> +{
> + asm volatile ("pushq %0\n\tpopfq" : : "rm" (eflags) : "flags");
> +}
> +
> +static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
> +{
> + ucontext_t *ctx = (ucontext_t *)ctx_void;
> + unsigned long ip = ctx->uc_mcontext.gregs[REG_RIP];
> +
> + if (((ip ^ 0xffffffffff600000UL) & ~0xfffUL) == 0)
> + num_vsyscall_traps++;
> +}
> +
> +static int test_native_vsyscall(void)
> +{
> + time_t tmp;
> + bool is_native;
> +
> + if (!vtime)
> + return 0;
> +
> + printf("[RUN]\tchecking for native vsyscall\n");
> + sethandler(SIGTRAP, sigtrap, 0);
> + set_eflags(get_eflags() | X86_EFLAGS_TF);
> + vtime(&tmp);
> + set_eflags(get_eflags() & ~X86_EFLAGS_TF);
> +
> + /*
> + * If vsyscalls are emulated, we expect a single trap in the
> + * vsyscall page -- the call instruction will trap with RIP
> + * pointing to the entry point before emulation takes over.
> + * In native mode, we expect two traps, since whatever code
> + * the vsyscall page contains will be more than just a ret
> + * instruction.
> + */
> + is_native = (num_vsyscall_traps > 1);
> +
> + printf("\tvsyscalls are %s (%d instructions in vsyscall page)\n",
> + (is_native ? "native" : "emulated"),
> + (int)num_vsyscall_traps);
> +
> + return 0;
> +}
> +#endif
> +
> +int main(int argc, char **argv)
> +{
> + int nerrs = 0;
> +
> + init_vdso();
> + nerrs += init_vsys();
> +
> + nerrs += test_gtod();
> + nerrs += test_time();
> + nerrs += test_getcpu(0);
> + nerrs += test_getcpu(1);
> +
> + sethandler(SIGSEGV, sigsegv, 0);
> + nerrs += test_vsys_r();
> +
> +#ifdef __x86_64__
> + nerrs += test_native_vsyscall();
> +#endif
> +
> + return nerrs ? 1 : 0;
> +}
> --
> 2.13.6
>
--
Kees Cook
Pixel Security
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