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// SPDX-License-Identifier: GPL-2.0
/*
* iopl.c - Test case for a Linux on Xen 64-bit bug
* Copyright (c) 2015 Andrew Lutomirski
*/
#define _GNU_SOURCE
#include <err.h>
#include <stdio.h>
#include <stdint.h>
#include <signal.h>
#include <setjmp.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdbool.h>
#include <sched.h>
#include <sys/io.h>
static int nerrs = 0;
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");
}
static jmp_buf jmpbuf;
static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
{
siglongjmp(jmpbuf, 1);
}
int main(void)
{
cpu_set_t cpuset;
CPU_ZERO(&cpuset);
CPU_SET(0, &cpuset);
if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
err(1, "sched_setaffinity to CPU 0");
/* Probe for iopl support. Note that iopl(0) works even as nonroot. */
if (iopl(3) != 0) {
printf("[OK]\tiopl(3) failed (%d) -- try running as root\n",
errno);
return 0;
}
/* Restore our original state prior to starting the test. */
if (iopl(0) != 0)
err(1, "iopl(0)");
pid_t child = fork();
if (child == -1)
err(1, "fork");
if (child == 0) {
printf("\tchild: set IOPL to 3\n");
if (iopl(3) != 0)
err(1, "iopl");
printf("[RUN]\tchild: write to 0x80\n");
asm volatile ("outb %%al, $0x80" : : "a" (0));
return 0;
} else {
int status;
if (waitpid(child, &status, 0) != child ||
!WIFEXITED(status)) {
printf("[FAIL]\tChild died\n");
nerrs++;
} else if (WEXITSTATUS(status) != 0) {
printf("[FAIL]\tChild failed\n");
nerrs++;
} else {
printf("[OK]\tChild succeeded\n");
}
}
printf("[RUN]\tparent: write to 0x80 (should fail)\n");
sethandler(SIGSEGV, sigsegv, 0);
if (sigsetjmp(jmpbuf, 1) != 0) {
printf("[OK]\twrite was denied\n");
} else {
asm volatile ("outb %%al, $0x80" : : "a" (0));
printf("[FAIL]\twrite was allowed\n");
nerrs++;
}
/* Test the capability checks. */
printf("\tiopl(3)\n");
if (iopl(3) != 0)
err(1, "iopl(3)");
printf("\tDrop privileges\n");
if (setresuid(1, 1, 1) != 0) {
printf("[WARN]\tDropping privileges failed\n");
goto done;
}
printf("[RUN]\tiopl(3) unprivileged but with IOPL==3\n");
if (iopl(3) != 0) {
printf("[FAIL]\tiopl(3) should work if iopl is already 3 even if unprivileged\n");
nerrs++;
}
printf("[RUN]\tiopl(0) unprivileged\n");
if (iopl(0) != 0) {
printf("[FAIL]\tiopl(0) should work if iopl is already 3 even if unprivileged\n");
nerrs++;
}
printf("[RUN]\tiopl(3) unprivileged\n");
if (iopl(3) == 0) {
printf("[FAIL]\tiopl(3) should fail if when unprivileged if iopl==0\n");
nerrs++;
} else {
printf("[OK]\tFailed as expected\n");
}
done:
return nerrs ? 1 : 0;
}
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