debuggerd_handler: use syscall(__NR_get[pt]id) instead of get[pt]id.
bionic's cached values for getpid/gettid can be invalid if the crashing
process manually invoked clone to create a thread or process, which
will lead the crash_dump refusing to do anything, because it sees the
actual values.
Use the getpid/gettid syscalls directly to ensure correct values on
this end.
Bug: http://b/37769298
Test: debuggerd_test
Change-Id: I0b1e652beb1a66e564a48b88ed7fa971d61c6ff9
diff --git a/debuggerd/debuggerd_test.cpp b/debuggerd/debuggerd_test.cpp
index 568879e..0b4bbfb 100644
--- a/debuggerd/debuggerd_test.cpp
+++ b/debuggerd/debuggerd_test.cpp
@@ -29,6 +29,7 @@
#include <android-base/file.h>
#include <android-base/logging.h>
+#include <android-base/macros.h>
#include <android-base/parseint.h>
#include <android-base/properties.h>
#include <android-base/strings.h>
@@ -149,7 +150,7 @@
// Returns -1 if we fail to read a response from tombstoned, otherwise the received return code.
void FinishIntercept(int* result);
- void StartProcess(std::function<void()> function);
+ void StartProcess(std::function<void()> function, std::function<pid_t()> forker = fork);
void StartCrasher(const std::string& crash_type);
void FinishCrasher();
void AssertDeath(int signo);
@@ -195,14 +196,14 @@
}
}
-void CrasherTest::StartProcess(std::function<void()> function) {
+void CrasherTest::StartProcess(std::function<void()> function, std::function<pid_t()> forker) {
unique_fd read_pipe;
unique_fd crasher_read_pipe;
if (!Pipe(&crasher_read_pipe, &crasher_pipe)) {
FAIL() << "failed to create pipe: " << strerror(errno);
}
- crasher_pid = fork();
+ crasher_pid = forker();
if (crasher_pid == -1) {
FAIL() << "fork failed: " << strerror(errno);
} else if (crasher_pid == 0) {
@@ -527,6 +528,37 @@
ASSERT_MATCH(result, R"(#00 pc [0-9a-f]+\s+ /system/lib)" ARCH_SUFFIX R"(/libc.so \(tgkill)");
}
+TEST_F(CrasherTest, fake_pid) {
+ int intercept_result;
+ unique_fd output_fd;
+
+ // Prime the getpid/gettid caches.
+ UNUSED(getpid());
+ UNUSED(gettid());
+
+ std::function<pid_t()> clone_fn = []() {
+ return syscall(__NR_clone, SIGCHLD, nullptr, nullptr, nullptr, nullptr);
+ };
+ StartProcess(
+ []() {
+ ASSERT_NE(getpid(), syscall(__NR_getpid));
+ ASSERT_NE(gettid(), syscall(__NR_gettid));
+ raise(SIGSEGV);
+ },
+ clone_fn);
+
+ StartIntercept(&output_fd);
+ FinishCrasher();
+ AssertDeath(SIGSEGV);
+ FinishIntercept(&intercept_result);
+
+ ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+ std::string result;
+ ConsumeFd(std::move(output_fd), &result);
+ ASSERT_MATCH(result, R"(#00 pc [0-9a-f]+\s+ /system/lib)" ARCH_SUFFIX R"(/libc.so \(tgkill)");
+}
+
TEST(crash_dump, zombie) {
pid_t forkpid = fork();
diff --git a/debuggerd/handler/debuggerd_handler.cpp b/debuggerd/handler/debuggerd_handler.cpp
index 6e3e6ac..8fd6e11 100644
--- a/debuggerd/handler/debuggerd_handler.cpp
+++ b/debuggerd/handler/debuggerd_handler.cpp
@@ -61,6 +61,16 @@
#define CRASH_DUMP_PATH "/system/bin/" CRASH_DUMP_NAME
+// Wrappers that directly invoke the respective syscalls, in case the cached values are invalid.
+#pragma GCC poison getpid gettid
+static pid_t __getpid() {
+ return syscall(__NR_getpid);
+}
+
+static pid_t __gettid() {
+ return syscall(__NR_gettid);
+}
+
static inline void futex_wait(volatile void* ftx, int value) {
syscall(__NR_futex, ftx, FUTEX_WAIT, value, nullptr, nullptr, 0);
}
@@ -124,7 +134,7 @@
}
if (signum == DEBUGGER_SIGNAL) {
- async_safe_format_log(ANDROID_LOG_INFO, "libc", "Requested dump for tid %d (%s)", gettid(),
+ async_safe_format_log(ANDROID_LOG_INFO, "libc", "Requested dump for tid %d (%s)", __gettid(),
thread_name);
return;
}
@@ -177,7 +187,7 @@
}
async_safe_format_log(ANDROID_LOG_FATAL, "libc", "Fatal signal %d (%s)%s%s in tid %d (%s)",
- signum, signal_name, code_desc, addr_desc, gettid(), thread_name);
+ signum, signal_name, code_desc, addr_desc, __gettid(), thread_name);
}
/*
@@ -337,7 +347,7 @@
// rt_tgsigqueueinfo(2) to preserve SA_SIGINFO) will cause it to be delivered
// when our signal handler returns.
if (crash_dump_started || info->si_signo != DEBUGGER_SIGNAL) {
- int rc = syscall(SYS_rt_tgsigqueueinfo, getpid(), gettid(), info->si_signo, info);
+ int rc = syscall(SYS_rt_tgsigqueueinfo, __getpid(), __gettid(), info->si_signo, info);
if (rc != 0) {
fatal_errno("failed to resend signal during crash");
}
@@ -362,7 +372,7 @@
memset(&si, 0, sizeof(si));
si.si_signo = signal_number;
si.si_code = SI_USER;
- si.si_pid = getpid();
+ si.si_pid = __getpid();
si.si_uid = getuid();
info = &si;
} else if (info->si_code >= 0 || info->si_code == SI_TKILL) {
@@ -404,7 +414,7 @@
debugger_thread_info thread_info = {
.crash_dump_started = false,
.pseudothread_tid = -1,
- .crashing_tid = gettid(),
+ .crashing_tid = __gettid(),
.signal_number = signal_number,
.info = info
};