From 3a6c6012ba2b9ed662872ccaf7d276d56240943b Mon Sep 17 00:00:00 2001
From: Joshua Peraza <jperaza@chromium.org>
Date: Fri, 16 Aug 2019 17:09:58 -0700
Subject: [PATCH] linux: override exception thread ID

When a crash dump request is received over a socket, the message
includes a stack address of the thread requesting the dump. This can
be used to override the ExceptionInfo's thread ID which may be
incorrect in the handler's PID namespace.

Bug: crashpad:286
Change-Id: I053cf709c5eeefb73b31328f16a806510e1bd35d
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/1759280
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
---
 handler/linux/crash_report_exception_handler.cc | 13 +++++++++----
 snapshot/linux/process_snapshot_linux.cc        |  7 ++++++-
 snapshot/linux/process_snapshot_linux.h         |  7 ++++++-
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/handler/linux/crash_report_exception_handler.cc b/handler/linux/crash_report_exception_handler.cc
index 1688df79..875afec3 100644
--- a/handler/linux/crash_report_exception_handler.cc
+++ b/handler/linux/crash_report_exception_handler.cc
@@ -95,13 +95,18 @@ bool CrashReportExceptionHandler::HandleExceptionWithConnection(
     return false;
   }
 
-  if (requesting_thread_id && requesting_thread_stack_address) {
-    *requesting_thread_id = process_snapshot.FindThreadWithStackAddress(
+  pid_t local_requesting_thread_id = -1;
+  if (requesting_thread_stack_address) {
+    local_requesting_thread_id = process_snapshot.FindThreadWithStackAddress(
         requesting_thread_stack_address);
   }
 
-  if (!process_snapshot.InitializeException(
-          info.exception_information_address)) {
+  if (requesting_thread_id) {
+    *requesting_thread_id = local_requesting_thread_id;
+  }
+
+  if (!process_snapshot.InitializeException(info.exception_information_address,
+                                            local_requesting_thread_id)) {
     Metrics::ExceptionCaptureResult(
         Metrics::CaptureResult::kExceptionInitializationFailed);
     return false;
diff --git a/snapshot/linux/process_snapshot_linux.cc b/snapshot/linux/process_snapshot_linux.cc
index bada3a95..35f870ec 100644
--- a/snapshot/linux/process_snapshot_linux.cc
+++ b/snapshot/linux/process_snapshot_linux.cc
@@ -64,7 +64,8 @@ pid_t ProcessSnapshotLinux::FindThreadWithStackAddress(
 }
 
 bool ProcessSnapshotLinux::InitializeException(
-    LinuxVMAddress exception_info_address) {
+    LinuxVMAddress exception_info_address,
+    pid_t exception_thread_id) {
   INITIALIZATION_STATE_DCHECK_VALID(initialized_);
   DCHECK(!exception_);
 
@@ -75,6 +76,10 @@ bool ProcessSnapshotLinux::InitializeException(
     return false;
   }
 
+  if (exception_thread_id >= 0) {
+    info.thread_id = exception_thread_id;
+  }
+
   exception_.reset(new internal::ExceptionSnapshotLinux());
   if (!exception_->Initialize(&process_reader_,
                               info.siginfo_address,
diff --git a/snapshot/linux/process_snapshot_linux.h b/snapshot/linux/process_snapshot_linux.h
index 705cb5f9..06b72aff 100644
--- a/snapshot/linux/process_snapshot_linux.h
+++ b/snapshot/linux/process_snapshot_linux.h
@@ -70,7 +70,12 @@ class ProcessSnapshotLinux final : public ProcessSnapshot {
   //!
   //! \param[in] exception_info The address of an ExceptionInformation in the
   //!     target process' address space.
-  bool InitializeException(LinuxVMAddress exception_info);
+  //! \param[in] exception_thread_id The thread ID to assocaite the thread with.
+  //!     Optional. If -1, the exception thread will be identified by the
+  //!     ExceptionInformation struct which contains the thread ID in the target
+  //!     process' namespace.
+  bool InitializeException(LinuxVMAddress exception_info,
+                           pid_t exception_thread_id = -1);
 
   //! \brief Sets the value to be returned by ReportID().
   //!