Prevent crashes if a map cannot be created.
Under some conditions, /proc/<pid>/maps might return nothing. If we
try and unwind in this case, we'll crash. Check this case and fail
the unwind.
Add checks that no other functions try and use map_ without
checking for nullptr.
Add logging when an unwind fails so it's clear what happened.
Bug: 21162746
Change-Id: I56ce51dda0cfc9db20475a441f118108196aa07c
diff --git a/debuggerd/backtrace.cpp b/debuggerd/backtrace.cpp
index c2a1dbc..79ee4e5 100644
--- a/debuggerd/backtrace.cpp
+++ b/debuggerd/backtrace.cpp
@@ -14,6 +14,8 @@
* limitations under the License.
*/
+#define LOG_TAG "DEBUG"
+
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
@@ -27,6 +29,8 @@
#include <sys/ptrace.h>
#include <backtrace/Backtrace.h>
+
+#include <log/log.h>
#include <UniquePtr.h>
#include "backtrace.h"
@@ -95,6 +99,8 @@
UniquePtr<Backtrace> backtrace(Backtrace::Create(tid, BACKTRACE_CURRENT_THREAD));
if (backtrace->Unwind(0)) {
dump_backtrace_to_log(backtrace.get(), log, " ");
+ } else {
+ ALOGE("Unwind failed: tid = %d", tid);
}
if (!attached && ptrace(PTRACE_DETACH, tid, 0, 0) != 0) {
diff --git a/debuggerd/tombstone.cpp b/debuggerd/tombstone.cpp
index b7e6b17..4c804ee 100644
--- a/debuggerd/tombstone.cpp
+++ b/debuggerd/tombstone.cpp
@@ -448,6 +448,8 @@
UniquePtr<Backtrace> backtrace(Backtrace::Create(pid, new_tid, map));
if (backtrace->Unwind(0)) {
dump_backtrace_and_stack(backtrace.get(), log);
+ } else {
+ ALOGE("Unwind of sibling failed: pid = %d, tid = %d", pid, new_tid);
}
log->current_tid = log->crashed_tid;
@@ -650,9 +652,13 @@
dump_registers(log, tid);
if (backtrace->Unwind(0)) {
dump_backtrace_and_stack(backtrace.get(), log);
+ } else {
+ ALOGE("Unwind failed: pid = %d, tid = %d", pid, tid);
}
dump_memory_and_code(log, tid);
- dump_all_maps(backtrace.get(), map.get(), log, tid);
+ if (map.get() != nullptr) {
+ dump_all_maps(backtrace.get(), map.get(), log, tid);
+ }
if (want_logs) {
dump_logs(log, pid, 5);
diff --git a/libbacktrace/Backtrace.cpp b/libbacktrace/Backtrace.cpp
index 4e4003e..128bb04 100644
--- a/libbacktrace/Backtrace.cpp
+++ b/libbacktrace/Backtrace.cpp
@@ -114,7 +114,9 @@
}
void Backtrace::FillInMap(uintptr_t pc, backtrace_map_t* map) {
- map_->FillIn(pc, map);
+ if (map_ != nullptr) {
+ map_->FillIn(pc, map);
+ }
}
Backtrace* Backtrace::Create(pid_t pid, pid_t tid, BacktraceMap* map) {
diff --git a/libbacktrace/BacktraceCurrent.cpp b/libbacktrace/BacktraceCurrent.cpp
index 14f04de..95cd4d1 100644
--- a/libbacktrace/BacktraceCurrent.cpp
+++ b/libbacktrace/BacktraceCurrent.cpp
@@ -65,6 +65,11 @@
}
bool BacktraceCurrent::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
+ if (GetMap() == nullptr) {
+ // Without a map object, we can't do anything.
+ return false;
+ }
+
if (ucontext) {
return UnwindFromContext(num_ignore_frames, ucontext);
}
diff --git a/libbacktrace/UnwindPtrace.cpp b/libbacktrace/UnwindPtrace.cpp
index a7c3de5..07c2430 100644
--- a/libbacktrace/UnwindPtrace.cpp
+++ b/libbacktrace/UnwindPtrace.cpp
@@ -48,6 +48,11 @@
}
bool UnwindPtrace::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
+ if (GetMap() == nullptr) {
+ // Without a map object, we can't do anything.
+ return false;
+ }
+
if (ucontext) {
BACK_LOGW("Unwinding from a specified context not supported yet.");
return false;