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gvisor/test/syscalls/linux/ptrace.cc

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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <elf.h>
#include <signal.h>
#include <stddef.h>
#include <sys/ptrace.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/user.h>
#include <sys/wait.h>
#include <unistd.h>
#include <iostream>
#include <utility>
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "test/util/logging.h"
#include "test/util/multiprocess_util.h"
#include "test/util/signal_util.h"
#include "test/util/test_util.h"
#include "test/util/thread_util.h"
#include "test/util/time_util.h"
DEFINE_bool(ptrace_test_execve_child, false,
"If true, run the "
"PtraceExecveTest_Execve_GetRegs_PeekUser_SIGKILL_TraceClone_"
"TraceExit child workload.");
namespace gvisor {
namespace testing {
namespace {
// PTRACE_GETSIGMASK and PTRACE_SETSIGMASK are not defined until glibc 2.23
// (fb53a27c5741 "Add new header definitions from Linux 4.4 (plus older ptrace
// definitions)").
constexpr auto kPtraceGetSigMask = static_cast<__ptrace_request>(0x420a);
constexpr auto kPtraceSetSigMask = static_cast<__ptrace_request>(0x420b);
// PTRACE_SYSEMU is not defined until glibc 2.27 (c48831d0eebf "linux/x86: sync
// sys/ptrace.h with Linux 4.14 [BZ #22433]").
constexpr auto kPtraceSysemu = static_cast<__ptrace_request>(31);
// PTRACE_EVENT_STOP is not defined until glibc 2.26 (3f67d1a7021e "Add Linux
// PTRACE_EVENT_STOP").
constexpr int kPtraceEventStop = 128;
// Sends sig to the current process with tgkill(2).
//
// glibc's raise(2) may change the signal mask before sending the signal. These
// extra syscalls make tests of syscall, signal interception, etc. difficult to
// write.
void RaiseSignal(int sig) {
pid_t pid = getpid();
TEST_PCHECK(pid > 0);
pid_t tid = gettid();
TEST_PCHECK(tid > 0);
TEST_PCHECK(tgkill(pid, tid, sig) == 0);
}
// Returns the Yama ptrace scope.
PosixErrorOr<int> YamaPtraceScope() {
constexpr char kYamaPtraceScopePath[] = "/proc/sys/kernel/yama/ptrace_scope";
ASSIGN_OR_RETURN_ERRNO(bool exists, Exists(kYamaPtraceScopePath));
if (!exists) {
// File doesn't exist means no Yama, so the scope is disabled -> 0.
return 0;
}
std::string contents;
RETURN_IF_ERRNO(GetContents(kYamaPtraceScopePath, &contents));
int scope;
if (!absl::SimpleAtoi(contents, &scope)) {
return PosixError(EINVAL, absl::StrCat(contents, ": not a valid number"));
}
return scope;
}
TEST(PtraceTest, AttachSelf) {
EXPECT_THAT(ptrace(PTRACE_ATTACH, gettid(), 0, 0),
SyscallFailsWithErrno(EPERM));
}
TEST(PtraceTest, AttachSameThreadGroup) {
pid_t const tid = gettid();
ScopedThread([&] {
EXPECT_THAT(ptrace(PTRACE_ATTACH, tid, 0, 0), SyscallFailsWithErrno(EPERM));
});
}
TEST(PtraceTest, AttachParent_PeekData_PokeData_SignalSuppression) {
// Yama prevents attaching to a parent. Skip the test if the scope is anything
// except disabled.
SKIP_IF(ASSERT_NO_ERRNO_AND_VALUE(YamaPtraceScope()) > 0);
constexpr long kBeforePokeDataValue = 10;
constexpr long kAfterPokeDataValue = 20;
volatile long word = kBeforePokeDataValue;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Attach to the parent.
pid_t const parent_pid = getppid();
TEST_PCHECK(ptrace(PTRACE_ATTACH, parent_pid, 0, 0) == 0);
MaybeSave();
// Block until the parent enters signal-delivery-stop as a result of the
// SIGSTOP sent by PTRACE_ATTACH.
int status;
TEST_PCHECK(waitpid(parent_pid, &status, 0) == parent_pid);
MaybeSave();
TEST_CHECK(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP);
// Replace the value of word in the parent process with kAfterPokeDataValue.
long const parent_word = ptrace(PTRACE_PEEKDATA, parent_pid, &word, 0);
MaybeSave();
TEST_CHECK(parent_word == kBeforePokeDataValue);
TEST_PCHECK(
ptrace(PTRACE_POKEDATA, parent_pid, &word, kAfterPokeDataValue) == 0);
MaybeSave();
// Detach from the parent and suppress the SIGSTOP. If the SIGSTOP is not
// suppressed, the parent will hang in group-stop, causing the test to time
// out.
TEST_PCHECK(ptrace(PTRACE_DETACH, parent_pid, 0, 0) == 0);
MaybeSave();
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to complete.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
// Check that the child's PTRACE_POKEDATA was effective.
EXPECT_EQ(kAfterPokeDataValue, word);
}
TEST(PtraceTest, GetSigMask) {
// glibc and the Linux kernel define a sigset_t with different sizes. To avoid
// creating a kernel_sigset_t and recreating all the modification functions
// (sigemptyset, etc), we just hardcode the kernel sigset size.
constexpr int kSizeofKernelSigset = 8;
constexpr int kBlockSignal = SIGUSR1;
sigset_t blocked;
sigemptyset(&blocked);
sigaddset(&blocked, kBlockSignal);
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Install a signal handler for kBlockSignal to avoid termination and block
// it.
TEST_PCHECK(signal(kBlockSignal, +[](int signo) {}) != SIG_ERR);
MaybeSave();
TEST_PCHECK(sigprocmask(SIG_SETMASK, &blocked, nullptr) == 0);
MaybeSave();
// Enable tracing.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
// This should be blocked.
RaiseSignal(kBlockSignal);
// This should be suppressed by parent, who will change signal mask in the
// meantime, which means kBlockSignal should be delivered once this resumes.
RaiseSignal(SIGSTOP);
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Get current signal mask.
sigset_t set;
EXPECT_THAT(ptrace(kPtraceGetSigMask, child_pid, kSizeofKernelSigset, &set),
SyscallSucceeds());
EXPECT_THAT(blocked, EqualsSigset(set));
// Try to get current signal mask with bad size argument.
EXPECT_THAT(ptrace(kPtraceGetSigMask, child_pid, 0, nullptr),
SyscallFailsWithErrno(EINVAL));
// Try to set bad signal mask.
sigset_t* bad_addr = reinterpret_cast<sigset_t*>(-1);
EXPECT_THAT(
ptrace(kPtraceSetSigMask, child_pid, kSizeofKernelSigset, bad_addr),
SyscallFailsWithErrno(EFAULT));
// Set signal mask to empty set.
sigset_t set1;
sigemptyset(&set1);
EXPECT_THAT(ptrace(kPtraceSetSigMask, child_pid, kSizeofKernelSigset, &set1),
SyscallSucceeds());
// Suppress SIGSTOP and resume the child. It should re-enter
// signal-delivery-stop for kBlockSignal.
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == kBlockSignal)
<< " status " << status;
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
// Let's see that process exited normally.
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
}
TEST(PtraceTest, GetSiginfo_SetSiginfo_SignalInjection) {
constexpr int kOriginalSigno = SIGUSR1;
constexpr int kInjectedSigno = SIGUSR2;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Override all signal handlers.
struct sigaction sa = {};
sa.sa_handler = +[](int signo) { _exit(signo); };
TEST_PCHECK(sigfillset(&sa.sa_mask) == 0);
for (int signo = 1; signo < 32; signo++) {
if (signo == SIGKILL || signo == SIGSTOP) {
continue;
}
TEST_PCHECK(sigaction(signo, &sa, nullptr) == 0);
}
for (int signo = SIGRTMIN; signo <= SIGRTMAX; signo++) {
TEST_PCHECK(sigaction(signo, &sa, nullptr) == 0);
}
// Unblock all signals.
TEST_PCHECK(sigprocmask(SIG_UNBLOCK, &sa.sa_mask, nullptr) == 0);
MaybeSave();
// Send ourselves kOriginalSignal while ptraced and exit with the signal we
// actually receive via the signal handler, if any, or 0 if we don't receive
// a signal.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
RaiseSignal(kOriginalSigno);
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself kOriginalSigno and enter
// signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == kOriginalSigno)
<< " status " << status;
siginfo_t siginfo = {};
ASSERT_THAT(ptrace(PTRACE_GETSIGINFO, child_pid, 0, &siginfo),
SyscallSucceeds());
EXPECT_EQ(kOriginalSigno, siginfo.si_signo);
EXPECT_EQ(SI_TKILL, siginfo.si_code);
// Replace the signal with kInjectedSigno, and check that the child exits
// with kInjectedSigno, indicating that signal injection was successful.
siginfo.si_signo = kInjectedSigno;
ASSERT_THAT(ptrace(PTRACE_SETSIGINFO, child_pid, 0, &siginfo),
SyscallSucceeds());
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, kInjectedSigno),
SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == kInjectedSigno)
<< " status " << status;
}
TEST(PtraceTest, SIGKILLDoesNotCauseSignalDeliveryStop) {
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
RaiseSignal(SIGKILL);
TEST_CHECK_MSG(false, "Survived SIGKILL?");
_exit(1);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Expect the child to die to SIGKILL without entering signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSIGNALED(status) && WTERMSIG(status) == SIGKILL)
<< " status " << status;
}
TEST(PtraceTest, PtraceKill) {
constexpr int kOriginalSigno = SIGUSR1;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
// PTRACE_KILL only works if tracee has entered signal-delivery-stop.
RaiseSignal(kOriginalSigno);
TEST_CHECK_MSG(false, "Failed to kill the process?");
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself kOriginalSigno and enter
// signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == kOriginalSigno)
<< " status " << status;
ASSERT_THAT(ptrace(PTRACE_KILL, child_pid, 0, 0), SyscallSucceeds());
// Expect the child to die with SIGKILL.
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSIGNALED(status) && WTERMSIG(status) == SIGKILL)
<< " status " << status;
}
TEST(PtraceTest, GetRegSet) {
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Enable tracing.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
// Use kill explicitly because we check the syscall argument register below.
kill(getpid(), SIGSTOP);
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Get the general registers.
struct user_regs_struct regs;
struct iovec iov;
iov.iov_base = &regs;
iov.iov_len = sizeof(regs);
EXPECT_THAT(ptrace(PTRACE_GETREGSET, child_pid, NT_PRSTATUS, &iov),
SyscallSucceeds());
// Read exactly the full register set.
EXPECT_EQ(iov.iov_len, sizeof(regs));
#ifdef __x86_64__
// Child called kill(2), with SIGSTOP as arg 2.
EXPECT_EQ(regs.rsi, SIGSTOP);
#endif
// Suppress SIGSTOP and resume the child.
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
// Let's see that process exited normally.
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
}
TEST(PtraceTest, AttachingConvertsGroupStopToPtraceStop) {
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
while (true) {
pause();
}
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// SIGSTOP the child and wait for it to stop.
ASSERT_THAT(kill(child_pid, SIGSTOP), SyscallSucceeds());
int status;
ASSERT_THAT(waitpid(child_pid, &status, WUNTRACED),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Attach to the child and expect it to re-enter a traced group-stop despite
// already being stopped.
ASSERT_THAT(ptrace(PTRACE_ATTACH, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Verify that the child is ptrace-stopped by checking that it can receive
// ptrace commands requiring a ptrace-stop.
EXPECT_THAT(ptrace(PTRACE_SETOPTIONS, child_pid, 0, 0), SyscallSucceeds());
// Group-stop is distinguished from signal-delivery-stop by PTRACE_GETSIGINFO
// failing with EINVAL.
siginfo_t siginfo = {};
EXPECT_THAT(ptrace(PTRACE_GETSIGINFO, child_pid, 0, &siginfo),
SyscallFailsWithErrno(EINVAL));
// Detach from the child and expect it to stay stopped without a notification.
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, WUNTRACED | WNOHANG),
SyscallSucceedsWithValue(0));
// Sending it SIGCONT should cause it to leave its stop.
ASSERT_THAT(kill(child_pid, SIGCONT), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, WCONTINUED),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFCONTINUED(status)) << " status " << status;
// Clean up the child.
ASSERT_THAT(kill(child_pid, SIGKILL), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSIGNALED(status) && WTERMSIG(status) == SIGKILL)
<< " status " << status;
}
// Fixture for tests parameterized by whether or not to use PTRACE_O_TRACEEXEC.
class PtraceExecveTest : public ::testing::TestWithParam<bool> {
protected:
bool TraceExec() const { return GetParam(); }
};
TEST_P(PtraceExecveTest, Execve_GetRegs_PeekUser_SIGKILL_TraceClone_TraceExit) {
ExecveArray const owned_child_argv = {"/proc/self/exe",
"--ptrace_test_execve_child"};
char* const* const child_argv = owned_child_argv.get();
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process. The test relies on calling execve() in a non-leader
// thread; pthread_create() isn't async-signal-safe, so the safest way to
// do this is to execve() first, then enable tracing and run the expected
// child process behavior in the new subprocess.
execve(child_argv[0], child_argv, /* envp = */ nullptr);
TEST_PCHECK_MSG(false, "Survived execve to test child");
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Enable PTRACE_O_TRACECLONE so we can get the ID of the child's non-leader
// thread, PTRACE_O_TRACEEXIT so we can observe the leader's death, and
// PTRACE_O_TRACEEXEC if required by the test. (The leader doesn't call
// execve, but options should be inherited across clone.)
long opts = PTRACE_O_TRACECLONE | PTRACE_O_TRACEEXIT;
if (TraceExec()) {
opts |= PTRACE_O_TRACEEXEC;
}
ASSERT_THAT(ptrace(PTRACE_SETOPTIONS, child_pid, 0, opts), SyscallSucceeds());
// Suppress the SIGSTOP and wait for the child's leader thread to report
// PTRACE_EVENT_CLONE. Get the new thread's ID from the event.
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGTRAP | (PTRACE_EVENT_CLONE << 8), status >> 8);
unsigned long eventmsg;
ASSERT_THAT(ptrace(PTRACE_GETEVENTMSG, child_pid, 0, &eventmsg),
SyscallSucceeds());
pid_t const nonleader_tid = eventmsg;
pid_t const leader_tid = child_pid;
// The new thread should be ptraced and in signal-delivery-stop by SIGSTOP due
// to PTRACE_O_TRACECLONE.
//
// Before bf959931ddb88c4e4366e96dd22e68fa0db9527c "wait/ptrace: assume __WALL
// if the child is traced" (4.7) , waiting on it requires __WCLONE since, as a
// non-leader, its termination signal is 0. After, a standard wait is
// sufficient.
ASSERT_THAT(waitpid(nonleader_tid, &status, __WCLONE),
SyscallSucceedsWithValue(nonleader_tid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Resume both child threads.
for (pid_t const tid : {leader_tid, nonleader_tid}) {
ASSERT_THAT(ptrace(PTRACE_CONT, tid, 0, 0), SyscallSucceeds());
}
// The non-leader child thread should call execve, causing the leader thread
// to enter PTRACE_EVENT_EXIT with an apparent exit code of 0. At this point,
// the leader has not yet exited, so the non-leader should be blocked in
// execve.
ASSERT_THAT(waitpid(leader_tid, &status, 0),
SyscallSucceedsWithValue(leader_tid));
EXPECT_EQ(SIGTRAP | (PTRACE_EVENT_EXIT << 8), status >> 8);
ASSERT_THAT(ptrace(PTRACE_GETEVENTMSG, leader_tid, 0, &eventmsg),
SyscallSucceeds());
EXPECT_TRUE(WIFEXITED(eventmsg) && WEXITSTATUS(eventmsg) == 0)
<< " eventmsg " << eventmsg;
EXPECT_THAT(waitpid(nonleader_tid, &status, __WCLONE | WNOHANG),
SyscallSucceedsWithValue(0));
// Allow the leader to continue exiting. This should allow the non-leader to
// complete its execve, causing the original leader to be reaped without
// further notice and the non-leader to steal its ID.
ASSERT_THAT(ptrace(PTRACE_CONT, leader_tid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(leader_tid, &status, 0),
SyscallSucceedsWithValue(leader_tid));
if (TraceExec()) {
// If PTRACE_O_TRACEEXEC was enabled, the execing thread should be in
// PTRACE_EVENT_EXEC-stop, with the event message set to its old thread ID.
EXPECT_EQ(SIGTRAP | (PTRACE_EVENT_EXEC << 8), status >> 8);
ASSERT_THAT(ptrace(PTRACE_GETEVENTMSG, leader_tid, 0, &eventmsg),
SyscallSucceeds());
EXPECT_EQ(nonleader_tid, eventmsg);
} else {
// Otherwise, the execing thread should have received SIGTRAP and should now
// be in signal-delivery-stop.
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP)
<< " status " << status;
}
#ifdef __x86_64__
{
// CS should be 0x33, indicating an 64-bit binary.
constexpr uint64_t kAMD64UserCS = 0x33;
EXPECT_THAT(ptrace(PTRACE_PEEKUSER, leader_tid,
offsetof(struct user_regs_struct, cs), 0),
SyscallSucceedsWithValue(kAMD64UserCS));
struct user_regs_struct regs = {};
ASSERT_THAT(ptrace(PTRACE_GETREGS, leader_tid, 0, &regs),
SyscallSucceeds());
EXPECT_EQ(kAMD64UserCS, regs.cs);
}
#endif // defined(__x86_64__)
// PTRACE_O_TRACEEXIT should have been inherited across execve. Send SIGKILL,
// which should end the PTRACE_EVENT_EXEC-stop or signal-delivery-stop and
// leave the child in PTRACE_EVENT_EXIT-stop.
ASSERT_THAT(kill(leader_tid, SIGKILL), SyscallSucceeds());
ASSERT_THAT(waitpid(leader_tid, &status, 0),
SyscallSucceedsWithValue(leader_tid));
EXPECT_EQ(SIGTRAP | (PTRACE_EVENT_EXIT << 8), status >> 8);
ASSERT_THAT(ptrace(PTRACE_GETEVENTMSG, leader_tid, 0, &eventmsg),
SyscallSucceeds());
EXPECT_TRUE(WIFSIGNALED(eventmsg) && WTERMSIG(eventmsg) == SIGKILL)
<< " eventmsg " << eventmsg;
// End the PTRACE_EVENT_EXIT stop, allowing the child to exit.
ASSERT_THAT(ptrace(PTRACE_CONT, leader_tid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(leader_tid, &status, 0),
SyscallSucceedsWithValue(leader_tid));
EXPECT_TRUE(WIFSIGNALED(status) && WTERMSIG(status) == SIGKILL)
<< " status " << status;
}
[[noreturn]] void RunExecveChild() {
// Enable tracing, then raise SIGSTOP and expect our parent to suppress it.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
RaiseSignal(SIGSTOP);
MaybeSave();
// Call execve() in a non-leader thread. As long as execve() succeeds, what
// exactly we execve() shouldn't really matter, since the tracer should kill
// us after execve() completes.
ScopedThread t([&] {
ExecveArray const owned_child_argv = {"/proc/self/exe",
"--this_flag_shouldnt_exist"};
char* const* const child_argv = owned_child_argv.get();
execve(child_argv[0], child_argv, /* envp = */ nullptr);
TEST_PCHECK_MSG(false, "Survived execve? (thread)");
});
t.Join();
TEST_CHECK_MSG(false, "Survived execve? (main)");
_exit(1);
}
INSTANTIATE_TEST_SUITE_P(TraceExec, PtraceExecveTest, ::testing::Bool());
// This test has expectations on when syscall-enter/exit-stops occur that are
// violated if saving occurs, since saving interrupts all syscalls, causing
// premature syscall-exit.
TEST(PtraceTest,
ExitWhenParentIsNotTracer_Syscall_TraceVfork_TraceVforkDone_NoRandomSave) {
constexpr int kExitTraceeExitCode = 99;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Block SIGCHLD so it doesn't interrupt wait4.
sigset_t mask;
TEST_PCHECK(sigemptyset(&mask) == 0);
TEST_PCHECK(sigaddset(&mask, SIGCHLD) == 0);
TEST_PCHECK(sigprocmask(SIG_SETMASK, &mask, nullptr) == 0);
MaybeSave();
// Enable tracing, then raise SIGSTOP and expect our parent to suppress it.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
RaiseSignal(SIGSTOP);
MaybeSave();
// Spawn a vfork child that exits immediately, and reap it. Don't save
// after vfork since the parent expects to see wait4 as the next syscall.
pid_t const pid = vfork();
if (pid == 0) {
_exit(kExitTraceeExitCode);
}
TEST_PCHECK_MSG(pid > 0, "vfork failed");
int status;
TEST_PCHECK(wait4(pid, &status, 0, nullptr) > 0);
MaybeSave();
TEST_CHECK(WIFEXITED(status) && WEXITSTATUS(status) == kExitTraceeExitCode);
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(child_pid, SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Enable PTRACE_O_TRACEVFORK so we can get the ID of the grandchild,
// PTRACE_O_TRACEVFORKDONE so we can observe PTRACE_EVENT_VFORK_DONE, and
// PTRACE_O_TRACESYSGOOD so syscall-enter/exit-stops are unambiguously
// indicated by a stop signal of SIGTRAP|0x80 rather than just SIGTRAP.
ASSERT_THAT(ptrace(PTRACE_SETOPTIONS, child_pid, 0,
PTRACE_O_TRACEVFORK | PTRACE_O_TRACEVFORKDONE |
PTRACE_O_TRACESYSGOOD),
SyscallSucceeds());
// Suppress the SIGSTOP and wait for the child to report PTRACE_EVENT_VFORK.
// Get the new process' ID from the event.
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGTRAP | (PTRACE_EVENT_VFORK << 8), status >> 8);
unsigned long eventmsg;
ASSERT_THAT(ptrace(PTRACE_GETEVENTMSG, child_pid, 0, &eventmsg),
SyscallSucceeds());
pid_t const grandchild_pid = eventmsg;
// The grandchild should be traced by us and in signal-delivery-stop by
// SIGSTOP due to PTRACE_O_TRACEVFORK. This allows us to wait on it even
// though we're not its parent.
ASSERT_THAT(waitpid(grandchild_pid, &status, 0),
SyscallSucceedsWithValue(grandchild_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Resume the child with PTRACE_SYSCALL. Since the grandchild is still in
// signal-delivery-stop, the child should remain in vfork() waiting for the
// grandchild to exec or exit.
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
absl::SleepFor(absl::Seconds(1));
ASSERT_THAT(waitpid(child_pid, &status, WNOHANG),
SyscallSucceedsWithValue(0));
// Suppress the grandchild's SIGSTOP and wait for the grandchild to exit. Pass
// WNOWAIT to waitid() so that we don't acknowledge the grandchild's exit yet.
ASSERT_THAT(ptrace(PTRACE_CONT, grandchild_pid, 0, 0), SyscallSucceeds());
siginfo_t siginfo = {};
ASSERT_THAT(waitid(P_PID, grandchild_pid, &siginfo, WEXITED | WNOWAIT),
SyscallSucceeds());
EXPECT_EQ(SIGCHLD, siginfo.si_signo);
EXPECT_EQ(CLD_EXITED, siginfo.si_code);
EXPECT_EQ(kExitTraceeExitCode, siginfo.si_status);
EXPECT_EQ(grandchild_pid, siginfo.si_pid);
EXPECT_EQ(getuid(), siginfo.si_uid);
// The child should now be in PTRACE_EVENT_VFORK_DONE stop. The event
// message should still be the grandchild's PID.
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGTRAP | (PTRACE_EVENT_VFORK_DONE << 8), status >> 8);
ASSERT_THAT(ptrace(PTRACE_GETEVENTMSG, child_pid, 0, &eventmsg),
SyscallSucceeds());
EXPECT_EQ(grandchild_pid, eventmsg);
// Resume the child with PTRACE_SYSCALL again and expect it to enter
// syscall-exit-stop for vfork() or clone(), either of which should return the
// grandchild's PID from the syscall. Aside from PTRACE_O_TRACESYSGOOD,
// syscall-stops are distinguished from signal-delivery-stop by
// PTRACE_GETSIGINFO returning a siginfo for which si_code == SIGTRAP or
// SIGTRAP|0x80.
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == (SIGTRAP | 0x80))
<< " status " << status;
ASSERT_THAT(ptrace(PTRACE_GETSIGINFO, child_pid, 0, &siginfo),
SyscallSucceeds());
EXPECT_TRUE(siginfo.si_code == SIGTRAP || siginfo.si_code == (SIGTRAP | 0x80))
<< "si_code = " << siginfo.si_code;
#ifdef __x86_64__
{
struct user_regs_struct regs = {};
ASSERT_THAT(ptrace(PTRACE_GETREGS, child_pid, 0, &regs), SyscallSucceeds());
EXPECT_TRUE(regs.orig_rax == SYS_vfork || regs.orig_rax == SYS_clone)
<< "orig_rax = " << regs.orig_rax;
EXPECT_EQ(grandchild_pid, regs.rax);
}
#endif // defined(__x86_64__)
// After this point, the child will be making wait4 syscalls that will be
// interrupted by saving, so saving is not permitted. Note that this is
// explicitly released below once the grandchild exits.
DisableSave ds;
// Resume the child with PTRACE_SYSCALL again and expect it to enter
// syscall-enter-stop for wait4().
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == (SIGTRAP | 0x80))
<< " status " << status;
ASSERT_THAT(ptrace(PTRACE_GETSIGINFO, child_pid, 0, &siginfo),
SyscallSucceeds());
EXPECT_TRUE(siginfo.si_code == SIGTRAP || siginfo.si_code == (SIGTRAP | 0x80))
<< "si_code = " << siginfo.si_code;
#ifdef __x86_64__
{
EXPECT_THAT(ptrace(PTRACE_PEEKUSER, child_pid,
offsetof(struct user_regs_struct, orig_rax), 0),
SyscallSucceedsWithValue(SYS_wait4));
}
#endif // defined(__x86_64__)
// Resume the child with PTRACE_SYSCALL again. Since the grandchild is
// waiting for the tracer (us) to acknowledge its exit first, wait4 should
// block.
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
absl::SleepFor(absl::Seconds(1));
ASSERT_THAT(waitpid(child_pid, &status, WNOHANG),
SyscallSucceedsWithValue(0));
// Acknowledge the grandchild's exit.
ASSERT_THAT(waitpid(grandchild_pid, &status, 0),
SyscallSucceedsWithValue(grandchild_pid));
ds.reset();
// Now the child should enter syscall-exit-stop for wait4, returning with the
// grandchild's PID.
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == (SIGTRAP | 0x80))
<< " status " << status;
#ifdef __x86_64__
{
struct user_regs_struct regs = {};
ASSERT_THAT(ptrace(PTRACE_GETREGS, child_pid, 0, &regs), SyscallSucceeds());
EXPECT_EQ(SYS_wait4, regs.orig_rax);
EXPECT_EQ(grandchild_pid, regs.rax);
}
#endif // defined(__x86_64__)
// Detach from the child and wait for it to exit.
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
}
// These tests requires knowledge of architecture-specific syscall convention.
#ifdef __x86_64__
TEST(PtraceTest, Int3) {
switch (GvisorPlatform()) {
case Platform::kKVM:
// TODO(b/124248694): int3 isn't handled properly.
return;
default:
break;
}
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Enable tracing.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
// Interrupt 3 - trap to debugger
asm("int3");
_exit(56);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP)
<< " status " << status;
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
// The child should validate the injected return value and then exit normally.
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 56)
<< " status " << status;
}
TEST(PtraceTest, Sysemu_PokeUser) {
constexpr int kSysemuHelperFirstExitCode = 126;
constexpr uint64_t kSysemuInjectedExitGroupReturn = 42;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Enable tracing, then raise SIGSTOP and expect our parent to suppress it.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
RaiseSignal(SIGSTOP);
// Try to exit_group, expecting the tracer to skip the syscall and set its
// own return value.
int const rv = syscall(SYS_exit_group, kSysemuHelperFirstExitCode);
TEST_PCHECK_MSG(rv == kSysemuInjectedExitGroupReturn,
"exit_group returned incorrect value");
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Suppress the SIGSTOP and wait for the child to enter syscall-enter-stop
// for its first exit_group syscall.
ASSERT_THAT(ptrace(kPtraceSysemu, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP)
<< " status " << status;
struct user_regs_struct regs = {};
ASSERT_THAT(ptrace(PTRACE_GETREGS, child_pid, 0, &regs), SyscallSucceeds());
EXPECT_EQ(SYS_exit_group, regs.orig_rax);
EXPECT_EQ(-ENOSYS, regs.rax);
EXPECT_EQ(kSysemuHelperFirstExitCode, regs.rdi);
// Replace the exit_group return value, then resume the child, which should
// automatically skip the syscall.
ASSERT_THAT(
ptrace(PTRACE_POKEUSER, child_pid, offsetof(struct user_regs_struct, rax),
kSysemuInjectedExitGroupReturn),
SyscallSucceeds());
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, 0), SyscallSucceeds());
// The child should validate the injected return value and then exit normally.
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
}
// This test also cares about syscall-exit-stop.
TEST(PtraceTest, ERESTART_NoRandomSave) {
constexpr int kSigno = SIGUSR1;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
// Ignore, but unblock, kSigno.
struct sigaction sa = {};
sa.sa_handler = SIG_IGN;
TEST_PCHECK(sigfillset(&sa.sa_mask) == 0);
TEST_PCHECK(sigaction(kSigno, &sa, nullptr) == 0);
MaybeSave();
TEST_PCHECK(sigprocmask(SIG_UNBLOCK, &sa.sa_mask, nullptr) == 0);
MaybeSave();
// Enable tracing, then raise SIGSTOP and expect our parent to suppress it.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
RaiseSignal(SIGSTOP);
// Invoke the pause syscall, which normally should not return until we
// receive a signal that "either terminates the process or causes the
// invocation of a signal-catching function".
pause();
_exit(0);
}
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// After this point, the child's pause syscall will be interrupted by saving,
// so saving is not permitted. Note that this is explicitly released below
// once the child is stopped.
DisableSave ds;
// Suppress the SIGSTOP and wait for the child to enter syscall-enter-stop for
// its pause syscall.
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP)
<< " status " << status;
struct user_regs_struct regs = {};
ASSERT_THAT(ptrace(PTRACE_GETREGS, child_pid, 0, &regs), SyscallSucceeds());
EXPECT_EQ(SYS_pause, regs.orig_rax);
EXPECT_EQ(-ENOSYS, regs.rax);
// Resume the child with PTRACE_SYSCALL and expect it to block in the pause
// syscall.
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
absl::SleepFor(absl::Seconds(1));
ASSERT_THAT(waitpid(child_pid, &status, WNOHANG),
SyscallSucceedsWithValue(0));
// Send the child kSigno, causing it to return ERESTARTNOHAND and enter
// syscall-exit-stop from the pause syscall.
constexpr int ERESTARTNOHAND = 514;
ASSERT_THAT(kill(child_pid, kSigno), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP)
<< " status " << status;
ds.reset();
ASSERT_THAT(ptrace(PTRACE_GETREGS, child_pid, 0, &regs), SyscallSucceeds());
EXPECT_EQ(SYS_pause, regs.orig_rax);
EXPECT_EQ(-ERESTARTNOHAND, regs.rax);
// Replace the return value from pause with 0, causing pause to not be
// restarted despite kSigno being ignored.
ASSERT_THAT(ptrace(PTRACE_POKEUSER, child_pid,
offsetof(struct user_regs_struct, rax), 0),
SyscallSucceeds());
// Detach from the child and wait for it to exit.
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
}
#endif // defined(__x86_64__)
TEST(PtraceTest, Seize_Interrupt_Listen) {
volatile long child_should_spin = 1;
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
while (child_should_spin) {
SleepSafe(absl::Seconds(1));
}
_exit(1);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Attach to the child with PTRACE_SEIZE; doing so should not stop the child.
ASSERT_THAT(ptrace(PTRACE_SEIZE, child_pid, 0, 0), SyscallSucceeds());
int status;
EXPECT_THAT(waitpid(child_pid, &status, WNOHANG),
SyscallSucceedsWithValue(0));
// Stop the child with PTRACE_INTERRUPT.
ASSERT_THAT(ptrace(PTRACE_INTERRUPT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGTRAP | (kPtraceEventStop << 8), status >> 8);
// Unset child_should_spin to verify that the child never leaves the spin
// loop.
ASSERT_THAT(ptrace(PTRACE_POKEDATA, child_pid, &child_should_spin, 0),
SyscallSucceeds());
// Send SIGSTOP to the child, then resume it, allowing it to proceed to
// signal-delivery-stop.
ASSERT_THAT(kill(child_pid, SIGSTOP), SyscallSucceeds());
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// Release the child from signal-delivery-stop without suppressing the
// SIGSTOP, causing it to enter group-stop.
ASSERT_THAT(ptrace(PTRACE_CONT, child_pid, 0, SIGSTOP), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGSTOP | (kPtraceEventStop << 8), status >> 8);
// "The state of the tracee after PTRACE_LISTEN is somewhat of a gray area: it
// is not in any ptrace-stop (ptrace commands won't work on it, and it will
// deliver waitpid(2) notifications), but it also may be considered 'stopped'
// because it is not executing instructions (is not scheduled), and if it was
// in group-stop before PTRACE_LISTEN, it will not respond to signals until
// SIGCONT is received." - ptrace(2).
ASSERT_THAT(ptrace(PTRACE_LISTEN, child_pid, 0, 0), SyscallSucceeds());
EXPECT_THAT(ptrace(PTRACE_CONT, child_pid, 0, 0),
SyscallFailsWithErrno(ESRCH));
EXPECT_THAT(waitpid(child_pid, &status, WNOHANG),
SyscallSucceedsWithValue(0));
EXPECT_THAT(kill(child_pid, SIGTERM), SyscallSucceeds());
absl::SleepFor(absl::Seconds(1));
EXPECT_THAT(waitpid(child_pid, &status, WNOHANG),
SyscallSucceedsWithValue(0));
// Send SIGCONT to the child, causing it to leave group-stop and re-trap due
// to PTRACE_LISTEN.
EXPECT_THAT(kill(child_pid, SIGCONT), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGTRAP | (kPtraceEventStop << 8), status >> 8);
// Detach the child and expect it to exit due to the SIGTERM we sent while
// it was stopped by PTRACE_LISTEN.
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSIGNALED(status) && WTERMSIG(status) == SIGTERM)
<< " status " << status;
}
TEST(PtraceTest, Interrupt_Listen_RequireSeize) {
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
TEST_PCHECK(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
MaybeSave();
raise(SIGSTOP);
_exit(0);
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Wait for the child to send itself SIGSTOP and enter signal-delivery-stop.
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP)
<< " status " << status;
// PTRACE_INTERRUPT and PTRACE_LISTEN should fail since the child wasn't
// attached with PTRACE_SEIZE, leaving the child in signal-delivery-stop.
EXPECT_THAT(ptrace(PTRACE_INTERRUPT, child_pid, 0, 0),
SyscallFailsWithErrno(EIO));
EXPECT_THAT(ptrace(PTRACE_LISTEN, child_pid, 0, 0),
SyscallFailsWithErrno(EIO));
// Suppress SIGSTOP and detach from the child, expecting it to exit normally.
ASSERT_THAT(ptrace(PTRACE_DETACH, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0)
<< " status " << status;
}
TEST(PtraceTest, SeizeSetOptions) {
pid_t const child_pid = fork();
if (child_pid == 0) {
// In child process.
while (true) {
SleepSafe(absl::Seconds(1));
}
}
// In parent process.
ASSERT_THAT(child_pid, SyscallSucceeds());
// Attach to the child with PTRACE_SEIZE while setting PTRACE_O_TRACESYSGOOD.
ASSERT_THAT(ptrace(PTRACE_SEIZE, child_pid, 0, PTRACE_O_TRACESYSGOOD),
SyscallSucceeds());
// Stop the child with PTRACE_INTERRUPT.
ASSERT_THAT(ptrace(PTRACE_INTERRUPT, child_pid, 0, 0), SyscallSucceeds());
int status;
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_EQ(SIGTRAP | (kPtraceEventStop << 8), status >> 8);
// Resume the child with PTRACE_SYSCALL and wait for it to enter
// syscall-enter-stop. The stop signal status from the syscall stop should be
// SIGTRAP|0x80, reflecting PTRACE_O_TRACESYSGOOD.
ASSERT_THAT(ptrace(PTRACE_SYSCALL, child_pid, 0, 0), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
EXPECT_TRUE(WIFSTOPPED(status) && WSTOPSIG(status) == (SIGTRAP | 0x80))
<< " status " << status;
// Clean up the child.
ASSERT_THAT(kill(child_pid, SIGKILL), SyscallSucceeds());
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
if (WIFSTOPPED(status) && WSTOPSIG(status) == (SIGTRAP | 0x80)) {
// "SIGKILL kills even within system calls (syscall-exit-stop is not
// generated prior to death by SIGKILL). The net effect is that SIGKILL
// always kills the process (all its threads), even if some threads of the
// process are ptraced." - ptrace(2). This is technically true, but...
//
// When we send SIGKILL to the child, kernel/signal.c:complete_signal() =>
// signal_wake_up(resume=1) kicks the tracee out of the syscall-enter-stop.
// The pending SIGKILL causes the syscall to be skipped, but the child
// thread still reports syscall-exit before checking for pending signals; in
// current kernels, this is
// arch/x86/entry/common.c:syscall_return_slowpath() =>
// syscall_slow_exit_work() =>
// include/linux/tracehook.h:tracehook_report_syscall_exit() =>
// ptrace_report_syscall() => kernel/signal.c:ptrace_notify() =>
// ptrace_do_notify() => ptrace_stop().
//
// ptrace_stop() sets the task's state to TASK_TRACED and the task's
// exit_code to SIGTRAP|0x80 (passed by ptrace_report_syscall()), then calls
// freezable_schedule(). freezable_schedule() eventually reaches
// __schedule(), which detects signal_pending_state() due to the pending
// SIGKILL, sets the task's state back to TASK_RUNNING, and returns without
// descheduling. Thus, the task never enters syscall-exit-stop. However, if
// our wait4() => kernel/exit.c:wait_task_stopped() racily observes the
// TASK_TRACED state and the non-zero exit code set by ptrace_stop() before
// __schedule() sets the state back to TASK_RUNNING, it will return the
// task's exit_code as status W_STOPCODE(SIGTRAP|0x80). So we get a spurious
// syscall-exit-stop notification, and need to wait4() again for task exit.
//
// gVisor is not susceptible to this race because
// kernel.Task.waitCollectTraceeStopLocked() checks specifically for an
// active ptraceStop, which is not initiated if SIGKILL is pending.
std::cout << "Observed syscall-exit after SIGKILL";
ASSERT_THAT(waitpid(child_pid, &status, 0),
SyscallSucceedsWithValue(child_pid));
}
EXPECT_TRUE(WIFSIGNALED(status) && WTERMSIG(status) == SIGKILL)
<< " status " << status;
}
} // namespace
} // namespace testing
} // namespace gvisor
int main(int argc, char** argv) {
gvisor::testing::TestInit(&argc, &argv);
if (FLAGS_ptrace_test_execve_child) {
gvisor::testing::RunExecveChild();
}
return RUN_ALL_TESTS();
}
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