[compiler-rt] r285385 - [asan/lsan] Avoid possible deadlock in dynamic ASan runtime thread initialization.

[Maxim Ostapenko via llvm-commits]

Author: chefmax
Date: Fri Oct 28 01:49:53 2016
New Revision: 285385

URL: http://llvm.org/viewvc/llvm-project?rev=285385&view=rev
Log:
[asan/lsan] Avoid possible deadlock in dynamic ASan runtime thread initialization.

There is possible deadlock in dynamic ASan runtime when we dlopen() shared lib
which creates a thread at the global initialization stage. The scenario:

1) dlopen grabs a GI_pthread_mutex_lock in main thread.
2) main thread calls pthread_create, ASan intercepts it, calls real pthread_create
   and waits for the second thread to be "fully initialized".
3) Newly created thread tries to access a thread local disable_counter in LSan
   (to complete its "full initialization") and hangs in tls_get_addr_tail, because
   it also tries to acquire GI_pthread_mutex_lock.

The issue is reproducible on relative recent Glibc versions e.g. 2.23.

Differential Revision: https://reviews.llvm.org/D26028

Added:
    compiler-rt/trunk/test/asan/TestCases/Linux/pthread_create_from_constructor.cc
Modified:
    compiler-rt/trunk/lib/lsan/lsan_common.cc

Modified: compiler-rt/trunk/lib/lsan/lsan_common.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/lsan/lsan_common.cc?rev=285385&r1=285384&r2=285385&view=diff
==============================================================================
--- compiler-rt/trunk/lib/lsan/lsan_common.cc (original)
+++ compiler-rt/trunk/lib/lsan/lsan_common.cc Fri Oct 28 01:49:53 2016
@@ -32,6 +32,7 @@ namespace __lsan {
 // also to protect the global list of root regions.
 BlockingMutex global_mutex(LINKER_INITIALIZED);
 
+__attribute__((tls_model("initial-exec")))
 THREADLOCAL int disable_counter;
 bool DisabledInThisThread() { return disable_counter > 0; }
 void DisableInThisThread() { disable_counter++; }

Added: compiler-rt/trunk/test/asan/TestCases/Linux/pthread_create_from_constructor.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/asan/TestCases/Linux/pthread_create_from_constructor.cc?rev=285385&view=auto
==============================================================================
--- compiler-rt/trunk/test/asan/TestCases/Linux/pthread_create_from_constructor.cc (added)
+++ compiler-rt/trunk/test/asan/TestCases/Linux/pthread_create_from_constructor.cc Fri Oct 28 01:49:53 2016
@@ -0,0 +1,48 @@
+// Test that ASan doesn't deadlock in __interceptor_pthread_create called
+// from dlopened shared library constructor. The deadlock happens only in shared
+// ASan runtime with recent Glibc (2.23 fits) when __interceptor_pthread_create
+// grabs global Glibc's GL(dl_load_lock) and waits for tls_get_addr_tail that
+// also tries to acquire it.
+//
+// RUN: %clangxx_asan -DBUILD_SO=1 -fPIC -shared %s -o %t-so.so
+// RUN: %clangxx_asan %s -o %t
+// RUN: %run %t 2>&1
+
+// dlopen() can not be intercepted on Android
+// UNSUPPORTED: android
+
+#ifdef BUILD_SO
+
+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+
+void *threadFn(void *) {
+  fprintf(stderr, "thread started\n");
+  while (true) {
+    usleep(100000);
+  }
+  return 0;
+}
+
+void __attribute__((constructor)) startPolling() {
+  fprintf(stderr, "initializing library\n");
+  pthread_t t;
+  pthread_create(&t, 0, &threadFn, 0);
+  fprintf(stderr, "done\n");
+}
+
+#else
+
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <string>
+
+int main(int argc, char **argv) {
+  std::string path = std::string(argv[0]) + "-so.so";
+  void *handle = dlopen(path.c_str(), RTLD_LAZY);
+  if (!handle)
+    abort();
+  return 0;
+}
+#endif