[LSan] Detect dynamic loader by its base address.

[alekseyshl]

Summary

Whenever possible (Linux + glibc 2.16+), detect dynamic loader module by
its base address, not by the module name matching. The current name
matching approach fails on some configurations.

lib/lsan/lsan_common.cc

if (caller_pc == 0 || (param->skip_linker_allocations &&
       m.set_tag(kReachable);
       param->frontier->push_back(chunk);
     }
   }
 }
 
 // On Linux, handles dynamically allocated TLS blocks by treating all chunks
 // allocated from ld-linux.so as reachable.
+// On Linux, treats all chunks allocated from ld-linux.so as reachable, which
+// covers dynamically allocated TLS blocks, internal dynamic loader's loaded
+// modules accounting etc.
 // Dynamic TLS blocks contain the TLS variables of dynamically loaded modules.
 // They are allocated with a __libc_memalign() call in allocate_and_init()
 // (elf/dl-tls.c). Glibc won't tell us the address ranges occupied by those
 // blocks, but we can make sure they come from our own allocator by intercepting
 // __libc_memalign(). On top of that, there is no easy way to reach them. Their
 // addresses are stored in a dynamically allocated array (the DTV) which is
 // referenced from the static TLS. Unfortunately, we can't just rely on the DTV
 // being reachable from the static TLS, and the dynamic TLS being reachable from

lib/lsan/lsan_common_linux.cc

 #if CAN_SANITIZE_LEAKS && SANITIZER_LINUX
 #include <link.h>
 
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 
+#if SANITIZER_USE_GETAUXVAL
+#include <sys/auxv.h>
+#endif  // SANITIZER_USE_GETAUXVAL
+
 namespace __lsan {
 
 static const char kLinkerName[] = "ld";
 
 static char linker_placeholder[sizeof(LoadedModule)] ALIGNED(64);
 static LoadedModule *linker = nullptr;
 
-static bool IsLinker(const char* full_name) {
-  return LibraryNameIs(full_name, kLinkerName);
+static bool IsLinker(const LoadedModule& module) {
+#if SANITIZER_USE_GETAUXVAL
+  return module.base_address() == getauxval(AT_BASE);
+#else
+  return LibraryNameIs(module.full_name(), kLinkerName);
+#endif  // SANITIZER_USE_GETAUXVAL
 }
 
 __attribute__((tls_model("initial-exec")))
 THREADLOCAL int disable_counter;
 bool DisabledInThisThread() { return disable_counter > 0; }
 void DisableInThisThread() { disable_counter++; }
 void EnableInThisThread() {
   if (disable_counter == 0) {
     DisableCounterUnderflow();
   }
   disable_counter--;
 }
 
 void InitializePlatformSpecificModules() {
   ListOfModules modules;
   modules.init();
   for (LoadedModule &module : modules) {
-    if (!IsLinker(module.full_name())) continue;
+    if (!IsLinker(module))
+      continue;
     if (linker == nullptr) {
       linker = reinterpret_cast<LoadedModule *>(linker_placeholder);
       *linker = module;
       module = LoadedModule();
     } else {
       VReport(1, "LeakSanitizer: Multiple modules match \"%s\". "
-              "TLS will not be handled correctly.\n", kLinkerName);
+                 "TLS and other allocations originating from linker might be "
+                 "falsely reported as leaks.\n", kLinkerName);
       linker->clear();
       linker = nullptr;
       return;
     }
   }
   if (linker == nullptr) {
-    VReport(1, "LeakSanitizer: Dynamic linker not found. "
-               "TLS will not be handled correctly.\n");
+    VReport(1, "LeakSanitizer: Dynamic linker not found. TLS and other "
+               "allocations originating from linker might be falsely reported "
+                "as leaks.\n");
   }
 }
 
 static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size,
                                         void *data) {
   Frontier *frontier = reinterpret_cast<Frontier *>(data);
   for (uptr j = 0; j < info->dlpi_phnum; j++) {
     const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]);

lib/sanitizer_common/sanitizer_linux.cc

 }
 extern char **environ;  // provided by crt1
 #endif  // SANITIZER_FREEBSD
 
 #if !SANITIZER_ANDROID
 #include <sys/signal.h>
 #endif
 
-#ifndef __GLIBC_PREREQ
-#define __GLIBC_PREREQ(x, y) 0
-#endif
-
-#if SANITIZER_LINUX && __GLIBC_PREREQ(2, 16)
-# define SANITIZER_USE_GETAUXVAL 1
-#else
-# define SANITIZER_USE_GETAUXVAL 0
-#endif
-
 #if SANITIZER_USE_GETAUXVAL
 #include <sys/auxv.h>
 #endif
 
 #if SANITIZER_LINUX
 // <linux/time.h>
 struct kernel_timeval {
   long tv_sec;

lib/sanitizer_common/sanitizer_platform.h

 // dlopen mallocs "libgcc_s.so" string which confuses LSan, it fails to realize
 // that this allocation happens in dynamic linker and should be ignored.
 #if SANITIZER_PPC || defined(__thumb__)
 # define SANITIZER_SUPPRESS_LEAK_ON_PTHREAD_EXIT 1
 #else
 # define SANITIZER_SUPPRESS_LEAK_ON_PTHREAD_EXIT 0
 #endif
 
+#ifndef __GLIBC_PREREQ
+#define __GLIBC_PREREQ(x, y) 0
+#endif
+
+#if SANITIZER_LINUX && __GLIBC_PREREQ(2, 16)
+# define SANITIZER_USE_GETAUXVAL 1
+#else
+# define SANITIZER_USE_GETAUXVAL 0
+#endif
 
 #endif // SANITIZER_PLATFORM_H