Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
selftests: vDSO: ensure vgetrandom works in a time namespace
After verifying that vDSO getrandom does work, which ensures that the
RNG is initialized, test to see if it also works inside of a time
namespace. This is important to test, because the vvar pages get
swizzled around there. If the arch code isn't careful, the RNG will
appear uninitialized inside of a time namespace.
Because broken code makes the RNG appear uninitialized, test that
everything works by issuing a call to vgetrandom from a fork in a time
namespace, and use ptrace to ensure that the actual syscall getrandom
doesn't get called. If it doesn't get called, then the test succeeds.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+42
-1
+42
-1
tools/testing/selftests/vDSO/vdso_test_getrandom.c
+42
-1
tools/testing/selftests/vDSO/vdso_test_getrandom.c
···
16
16
#include <sys/mman.h>
17
17
#include <sys/random.h>
18
18
#include <sys/syscall.h>
19
+
#include <sys/ptrace.h>
20
+
#include <sys/wait.h>
19
21
#include <sys/types.h>
20
22
#include <linux/random.h>
23
+
#include <linux/compiler.h>
24
+
#include <linux/ptrace.h>
21
25
22
26
#include "../kselftest.h"
23
27
#include "parse_vdso.h"
···
243
239
static void kselftest(void)
244
240
{
245
241
uint8_t weird_size[1263];
242
+
pid_t child;
246
243
247
244
ksft_print_header();
248
-
ksft_set_plan(1);
245
+
ksft_set_plan(2);
249
246
250
247
for (size_t i = 0; i < 1000; ++i) {
251
248
ssize_t ret = vgetrandom(weird_size, sizeof(weird_size), 0);
···
255
250
}
256
251
257
252
ksft_test_result_pass("getrandom: PASS\n");
253
+
254
+
unshare(CLONE_NEWUSER);
255
+
assert(unshare(CLONE_NEWTIME) == 0);
256
+
child = fork();
257
+
assert(child >= 0);
258
+
if (!child) {
259
+
vgetrandom_init();
260
+
child = getpid();
261
+
assert(ptrace(PTRACE_TRACEME, 0, NULL, NULL) == 0);
262
+
assert(kill(child, SIGSTOP) == 0);
263
+
assert(vgetrandom(weird_size, sizeof(weird_size), 0) == sizeof(weird_size));
264
+
_exit(0);
265
+
}
266
+
for (;;) {
267
+
struct ptrace_syscall_info info = { 0 };
268
+
int status, ret;
269
+
assert(waitpid(child, &status, 0) >= 0);
270
+
if (WIFEXITED(status)) {
271
+
if (WEXITSTATUS(status) != 0)
272
+
exit(KSFT_FAIL);
273
+
break;
274
+
}
275
+
assert(WIFSTOPPED(status));
276
+
if (WSTOPSIG(status) == SIGSTOP)
277
+
assert(ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACESYSGOOD) == 0);
278
+
else if (WSTOPSIG(status) == (SIGTRAP | 0x80)) {
279
+
assert(ptrace(PTRACE_GET_SYSCALL_INFO, child, sizeof(info), &info) > 0);
280
+
if (info.op == PTRACE_SYSCALL_INFO_ENTRY && info.entry.nr == __NR_getrandom &&
281
+
info.entry.args[0] == (uintptr_t)weird_size && info.entry.args[1] == sizeof(weird_size))
282
+
exit(KSFT_FAIL);
283
+
}
284
+
assert(ptrace(PTRACE_SYSCALL, child, 0, 0) == 0);
285
+
}
286
+
287
+
ksft_test_result_pass("getrandom timens: PASS\n");
288
+
258
289
exit(KSFT_PASS);
259
290
}
260
291