// 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 = ®s; 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, ®s), 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, ®s), 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, ®s), 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, ®s), 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, ®s), 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, ®s), 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(); }