1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399
|
/* Tests for memory protection keys.
Copyright (C) 2017-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <inttypes.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <support/check.h>
#include <support/support.h>
#include <support/test-driver.h>
#include <support/xsignal.h>
#include <support/xthread.h>
#include <support/xunistd.h>
#include <sys/mman.h>
/* Used to force threads to wait until the main thread has set up the
keys as intended. */
static pthread_barrier_t barrier;
/* The keys used for testing. These have been allocated with access
rights set based on their array index. */
enum { key_count = 4 };
static int keys[key_count];
static volatile int *pages[key_count];
/* Used to report results from the signal handler. */
static volatile void *sigsegv_addr;
static volatile int sigsegv_code;
static volatile int sigsegv_pkey;
static sigjmp_buf sigsegv_jmp;
/* Used to handle expected read or write faults. */
static void
sigsegv_handler (int signum, siginfo_t *info, void *context)
{
sigsegv_addr = info->si_addr;
sigsegv_code = info->si_code;
sigsegv_pkey = info->si_pkey;
siglongjmp (sigsegv_jmp, 2);
}
static const struct sigaction sigsegv_sigaction =
{
.sa_flags = SA_RESETHAND | SA_SIGINFO,
.sa_sigaction = &sigsegv_handler,
};
/* Check if PAGE is readable (if !WRITE) or writable (if WRITE). */
static bool
check_page_access (int page, bool write)
{
/* This is needed to work around bug 22396: On x86-64, siglongjmp
does not restore the protection key access rights for the current
thread. We restore only the access rights for the keys under
test. (This is not a general solution to this problem, but it
allows testing to proceed after a fault.) */
unsigned saved_rights[key_count];
for (int i = 0; i < key_count; ++i)
saved_rights[i] = pkey_get (keys[i]);
volatile int *addr = pages[page];
if (test_verbose > 0)
{
printf ("info: checking access at %p (page %d) for %s\n",
addr, page, write ? "writing" : "reading");
}
int result = sigsetjmp (sigsegv_jmp, 1);
if (result == 0)
{
xsigaction (SIGSEGV, &sigsegv_sigaction, NULL);
if (write)
*addr = 3;
else
(void) *addr;
xsignal (SIGSEGV, SIG_DFL);
if (test_verbose > 0)
puts (" --> access allowed");
return true;
}
else
{
xsignal (SIGSEGV, SIG_DFL);
if (test_verbose > 0)
puts (" --> access denied");
TEST_COMPARE (result, 2);
TEST_COMPARE ((uintptr_t) sigsegv_addr, (uintptr_t) addr);
TEST_COMPARE (sigsegv_code, SEGV_PKUERR);
TEST_COMPARE (sigsegv_pkey, keys[page]);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_set (keys[i], saved_rights[i]), 0);
return false;
}
}
static volatile sig_atomic_t sigusr1_handler_ran;
/* Used to check that access is revoked in signal handlers. */
static void
sigusr1_handler (int signum)
{
TEST_COMPARE (signum, SIGUSR1);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_get (keys[i]), PKEY_DISABLE_ACCESS);
sigusr1_handler_ran = 1;
}
/* Used to report results from other threads. */
struct thread_result
{
int access_rights[key_count];
pthread_t next_thread;
};
/* Return the thread's access rights for the keys under test. */
static void *
get_thread_func (void *closure)
{
struct thread_result *result = xmalloc (sizeof (*result));
for (int i = 0; i < key_count; ++i)
result->access_rights[i] = pkey_get (keys[i]);
memset (&result->next_thread, 0, sizeof (result->next_thread));
return result;
}
/* Wait for initialization and then check that the current thread does
not have access through the keys under test. */
static void *
delayed_thread_func (void *closure)
{
bool check_access = *(bool *) closure;
pthread_barrier_wait (&barrier);
struct thread_result *result = get_thread_func (NULL);
if (check_access)
{
/* Also check directly. This code should not run with other
threads in parallel because of the SIGSEGV handler which is
installed by check_page_access. */
for (int i = 0; i < key_count; ++i)
{
TEST_VERIFY (!check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
}
result->next_thread = xpthread_create (NULL, get_thread_func, NULL);
return result;
}
static int
do_test (void)
{
long pagesize = xsysconf (_SC_PAGESIZE);
/* pkey_mprotect with key -1 should work even when there is no
protection key support. */
{
int *page = xmmap (NULL, pagesize, PROT_NONE,
MAP_ANONYMOUS | MAP_PRIVATE, -1);
TEST_COMPARE (pkey_mprotect (page, pagesize, PROT_READ | PROT_WRITE, -1),
0);
volatile int *vpage = page;
*vpage = 5;
TEST_COMPARE (*vpage, 5);
xmunmap (page, pagesize);
}
xpthread_barrier_init (&barrier, NULL, 2);
bool delayed_thread_check_access = true;
pthread_t delayed_thread = xpthread_create
(NULL, &delayed_thread_func, &delayed_thread_check_access);
keys[0] = pkey_alloc (0, 0);
if (keys[0] < 0)
{
if (errno == ENOSYS)
FAIL_UNSUPPORTED
("kernel does not support memory protection keys");
if (errno == EINVAL)
FAIL_UNSUPPORTED
("CPU does not support memory protection keys: %m");
FAIL_EXIT1 ("pkey_alloc: %m");
}
TEST_COMPARE (pkey_get (keys[0]), 0);
for (int i = 1; i < key_count; ++i)
{
keys[i] = pkey_alloc (0, i);
if (keys[i] < 0)
FAIL_EXIT1 ("pkey_alloc (0, %d): %m", i);
/* pkey_alloc is supposed to change the current thread's access
rights for the new key. */
TEST_COMPARE (pkey_get (keys[i]), i);
}
/* Check that all the keys have the expected access rights for the
current thread. */
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_get (keys[i]), i);
/* Allocate a test page for each key. */
for (int i = 0; i < key_count; ++i)
{
pages[i] = xmmap (NULL, pagesize, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1);
TEST_COMPARE (pkey_mprotect ((void *) pages[i], pagesize,
PROT_READ | PROT_WRITE, keys[i]), 0);
}
/* Check that the initial thread does not have access to the new
keys. */
{
pthread_barrier_wait (&barrier);
struct thread_result *result = xpthread_join (delayed_thread);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (result->access_rights[i],
PKEY_DISABLE_ACCESS);
struct thread_result *result2 = xpthread_join (result->next_thread);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (result->access_rights[i],
PKEY_DISABLE_ACCESS);
free (result);
free (result2);
}
/* Check that the current thread access rights are inherited by new
threads. */
{
pthread_t get_thread = xpthread_create (NULL, get_thread_func, NULL);
struct thread_result *result = xpthread_join (get_thread);
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (result->access_rights[i], i);
free (result);
}
for (int i = 0; i < key_count; ++i)
TEST_COMPARE (pkey_get (keys[i]), i);
/* Check that in a signal handler, there is no access. */
xsignal (SIGUSR1, &sigusr1_handler);
xraise (SIGUSR1);
xsignal (SIGUSR1, SIG_DFL);
TEST_COMPARE (sigusr1_handler_ran, 1);
/* The first key results in a writable page. */
TEST_VERIFY (check_page_access (0, false));
TEST_VERIFY (check_page_access (0, true));
/* The other keys do not. */
for (int i = 1; i < key_count; ++i)
{
if (test_verbose)
printf ("info: checking access for key %d, bits 0x%x\n",
i, pkey_get (keys[i]));
for (int j = 0; j < key_count; ++j)
TEST_COMPARE (pkey_get (keys[j]), j);
if (i & PKEY_DISABLE_ACCESS)
{
TEST_VERIFY (!check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
else
{
TEST_VERIFY (i & PKEY_DISABLE_WRITE);
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
}
/* But if we set the current thread's access rights, we gain
access. */
for (int do_write = 0; do_write < 2; ++do_write)
for (int allowed_key = 0; allowed_key < key_count; ++allowed_key)
{
for (int i = 0; i < key_count; ++i)
if (i == allowed_key)
{
if (do_write)
TEST_COMPARE (pkey_set (keys[i], 0), 0);
else
TEST_COMPARE (pkey_set (keys[i], PKEY_DISABLE_WRITE), 0);
}
else
TEST_COMPARE (pkey_set (keys[i], PKEY_DISABLE_ACCESS), 0);
if (test_verbose)
printf ("info: key %d is allowed access for %s\n",
allowed_key, do_write ? "writing" : "reading");
for (int i = 0; i < key_count; ++i)
if (i == allowed_key)
{
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (check_page_access (i, true) == do_write);
}
else
{
TEST_VERIFY (!check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
}
}
/* Restore access to all keys, and launch a thread which should
inherit that access. */
for (int i = 0; i < key_count; ++i)
{
TEST_COMPARE (pkey_set (keys[i], 0), 0);
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (check_page_access (i, true));
}
delayed_thread_check_access = false;
delayed_thread = xpthread_create
(NULL, delayed_thread_func, &delayed_thread_check_access);
TEST_COMPARE (pkey_free (keys[0]), 0);
/* Second pkey_free will fail because the key has already been
freed. */
TEST_COMPARE (pkey_free (keys[0]),-1);
TEST_COMPARE (errno, EINVAL);
for (int i = 1; i < key_count; ++i)
TEST_COMPARE (pkey_free (keys[i]), 0);
/* Check what happens to running threads which have access to
previously allocated protection keys. The implemented behavior
is somewhat dubious: Ideally, pkey_free should revoke access to
that key and pkey_alloc of the same (numeric) key should not
implicitly confer access to already-running threads, but this is
not what happens in practice. */
{
/* The limit is in place to avoid running indefinitely in case
there many keys available. */
int *keys_array = xcalloc (100000, sizeof (*keys_array));
int keys_allocated = 0;
while (keys_allocated < 100000)
{
int new_key = pkey_alloc (0, PKEY_DISABLE_WRITE);
if (new_key < 0)
{
/* No key reuse observed before running out of keys. */
TEST_COMPARE (errno, ENOSPC);
break;
}
for (int i = 0; i < key_count; ++i)
if (new_key == keys[i])
{
/* We allocated the key with disabled write access.
This should affect the protection state of the
existing page. */
TEST_VERIFY (check_page_access (i, false));
TEST_VERIFY (!check_page_access (i, true));
xpthread_barrier_wait (&barrier);
struct thread_result *result = xpthread_join (delayed_thread);
/* The thread which was launched before should still have
access to the key. */
TEST_COMPARE (result->access_rights[i], 0);
struct thread_result *result2
= xpthread_join (result->next_thread);
/* Same for a thread which is launched afterwards from
the old thread. */
TEST_COMPARE (result2->access_rights[i], 0);
free (result);
free (result2);
keys_array[keys_allocated++] = new_key;
goto after_key_search;
}
/* Save key for later deallocation. */
keys_array[keys_allocated++] = new_key;
}
after_key_search:
/* Deallocate the keys allocated for testing purposes. */
for (int j = 0; j < keys_allocated; ++j)
TEST_COMPARE (pkey_free (keys_array[j]), 0);
free (keys_array);
}
for (int i = 0; i < key_count; ++i)
xmunmap ((void *) pages[i], pagesize);
xpthread_barrier_destroy (&barrier);
return 0;
}
#include <support/test-driver.c>
|