From 14d7e0bb0f75066da5d2eff718b6d59215a02077 Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka@google.com>
Date: Wed, 13 Dec 2023 13:09:36 -0800
Subject: [lsan] Install `pthread_atfork` (#75281)

This prevents deadlocks in forked process on essencial
runtime components.
---
 compiler-rt/lib/lsan/lsan.cpp                          |  1 +
 compiler-rt/lib/lsan/lsan.h                            |  1 +
 compiler-rt/lib/lsan/lsan_common.cpp                   |  3 +++
 compiler-rt/lib/lsan/lsan_common.h                     |  4 ++++
 compiler-rt/lib/lsan/lsan_fuchsia.cpp                  |  1 +
 compiler-rt/lib/lsan/lsan_posix.cpp                    | 18 ++++++++++++++++++
 .../sanitizer_common/TestCases/Posix/fork_threaded.c   |  2 +-
 7 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/compiler-rt/lib/lsan/lsan.cpp b/compiler-rt/lib/lsan/lsan.cpp
index 6b22360..7a27b60 100644
--- a/compiler-rt/lib/lsan/lsan.cpp
+++ b/compiler-rt/lib/lsan/lsan.cpp
@@ -101,6 +101,7 @@ extern "C" void __lsan_init() {
   InstallDeadlySignalHandlers(LsanOnDeadlySignal);
   InitializeMainThread();
   InstallAtExitCheckLeaks();
+  InstallAtForkHandler();
 
   InitializeCoverage(common_flags()->coverage, common_flags()->coverage_dir);
 
diff --git a/compiler-rt/lib/lsan/lsan.h b/compiler-rt/lib/lsan/lsan.h
index 757edec..0074ad5 100644
--- a/compiler-rt/lib/lsan/lsan.h
+++ b/compiler-rt/lib/lsan/lsan.h
@@ -40,6 +40,7 @@ void InitializeInterceptors();
 void ReplaceSystemMalloc();
 void LsanOnDeadlySignal(int signo, void *siginfo, void *context);
 void InstallAtExitCheckLeaks();
+void InstallAtForkHandler();
 
 #define ENSURE_LSAN_INITED        \
   do {                            \
diff --git a/compiler-rt/lib/lsan/lsan_common.cpp b/compiler-rt/lib/lsan/lsan_common.cpp
index 8b1af5b..e24839c 100644
--- a/compiler-rt/lib/lsan/lsan_common.cpp
+++ b/compiler-rt/lib/lsan/lsan_common.cpp
@@ -42,6 +42,9 @@ namespace __lsan {
 // also to protect the global list of root regions.
 static Mutex global_mutex;
 
+void LockGlobal() SANITIZER_ACQUIRE(global_mutex) { global_mutex.Lock(); }
+void UnlockGlobal() SANITIZER_RELEASE(global_mutex) { global_mutex.Unlock(); }
+
 Flags lsan_flags;
 
 void DisableCounterUnderflow() {
diff --git a/compiler-rt/lib/lsan/lsan_common.h b/compiler-rt/lib/lsan/lsan_common.h
index d3e7683..c598b62 100644
--- a/compiler-rt/lib/lsan/lsan_common.h
+++ b/compiler-rt/lib/lsan/lsan_common.h
@@ -120,6 +120,10 @@ void GetRunningThreadsLocked(InternalMmapVector<tid_t> *threads);
 void LockAllocator();
 void UnlockAllocator();
 
+// Lock/unlock global mutext.
+void LockGlobal();
+void UnlockGlobal();
+
 // Returns the address range occupied by the global allocator object.
 void GetAllocatorGlobalRange(uptr *begin, uptr *end);
 // If p points into a chunk that has been allocated to the user, returns its
diff --git a/compiler-rt/lib/lsan/lsan_fuchsia.cpp b/compiler-rt/lib/lsan/lsan_fuchsia.cpp
index 4edac97..ba59bc9 100644
--- a/compiler-rt/lib/lsan/lsan_fuchsia.cpp
+++ b/compiler-rt/lib/lsan/lsan_fuchsia.cpp
@@ -80,6 +80,7 @@ void GetAllThreadAllocatorCachesLocked(InternalMmapVector<uptr> *caches) {
 // On Fuchsia, leak detection is done by a special hook after atexit hooks.
 // So this doesn't install any atexit hook like on other platforms.
 void InstallAtExitCheckLeaks() {}
+void InstallAtForkHandler() {}
 
 // ASan defines this to check its `halt_on_error` flag.
 bool UseExitcodeOnLeak() { return true; }
diff --git a/compiler-rt/lib/lsan/lsan_posix.cpp b/compiler-rt/lib/lsan/lsan_posix.cpp
index 732b8af..3677f01 100644
--- a/compiler-rt/lib/lsan/lsan_posix.cpp
+++ b/compiler-rt/lib/lsan/lsan_posix.cpp
@@ -14,6 +14,8 @@
 #include "sanitizer_common/sanitizer_platform.h"
 
 #if SANITIZER_POSIX
+#  include <pthread.h>
+
 #  include "lsan.h"
 #  include "lsan_allocator.h"
 #  include "lsan_thread.h"
@@ -98,6 +100,22 @@ void InstallAtExitCheckLeaks() {
     Atexit(DoLeakCheck);
 }
 
+void InstallAtForkHandler() {
+  auto before = []() {
+    LockGlobal();
+    LockThreads();
+    LockAllocator();
+    StackDepotLockAll();
+  };
+  auto after = []() {
+    StackDepotUnlockAll();
+    UnlockAllocator();
+    UnlockThreads();
+    UnlockGlobal();
+  };
+  pthread_atfork(before, after, after);
+}
+
 }  // namespace __lsan
 
 #endif  // SANITIZER_POSIX
diff --git a/compiler-rt/test/sanitizer_common/TestCases/Posix/fork_threaded.c b/compiler-rt/test/sanitizer_common/TestCases/Posix/fork_threaded.c
index eaa1a04..7592269 100644
--- a/compiler-rt/test/sanitizer_common/TestCases/Posix/fork_threaded.c
+++ b/compiler-rt/test/sanitizer_common/TestCases/Posix/fork_threaded.c
@@ -1,6 +1,6 @@
 // RUN: %clang -O0 %s -o %t && %env_tool_opts=die_after_fork=0 %run %t
 
-// UNSUPPORTED: asan, lsan, hwasan
+// UNSUPPORTED: asan, hwasan
 
 // The test uses pthread barriers which are not available on Darwin.
 // UNSUPPORTED: darwin
-- 
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