[PATCH] D34227: [asan] Return allow_user_segv_handler=0 to fix compatibility issues.

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka created this revision.
Herald added a subscriber: kubamracek.

After r303941 it was not possible to setup ASAN_OPTIONS to have the same
behavior for pre r303941 and post r303941 builds.
Pre r303941 Asan does not accept handle_sigbus=2.
Post r303941 Asan does not accept allow_user_segv_handler.

This fix ignores allow_user_segv_handler=1, but for allow_user_segv_handler=0
it will upgrade flags like handle_sigbus=1 to handle_sigbus=2. So user can set
ASAN_OPTIONS=allow_user_segv_handler=0 and have same behavior on old and new
clang builds (except range from r303941 to this revision).

In future users which need to prevent third party handlers should switch to
handle_sigbus=2 and remove allow_user_segv_handler as soon as suport of older
builds is not needed.

Related bugs:

  https://github.com/google/oss-fuzz/issues/675
  https://bugs.chromium.org/p/chromium/issues/detail?id=731130


https://reviews.llvm.org/D34227

Files:
  lib/sanitizer_common/sanitizer_flags.inc
  lib/sanitizer_common/sanitizer_linux.cc
  lib/sanitizer_common/sanitizer_mac.cc
  test/asan/TestCases/Posix/allow_user_segv.cc


Index: test/asan/TestCases/Posix/allow_user_segv.cc
===================================================================
--- test/asan/TestCases/Posix/allow_user_segv.cc
+++ test/asan/TestCases/Posix/allow_user_segv.cc
@@ -10,6 +10,9 @@
 // RUN: %clangxx_asan -O0 %s -o %t && %env_asan_opts=handle_segv=2 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK2
 // RUN: %clangxx_asan -O2 %s -o %t && %env_asan_opts=handle_segv=2 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK2
 
+// RUN: %clangxx_asan -O0 %s -o %t && %env_asan_opts=handle_segv=1:allow_user_segv_handler=0 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK2
+// RUN: %clangxx_asan -O2 %s -o %t && %env_asan_opts=handle_segv=1:allow_user_segv_handler=0 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK2
+
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
Index: lib/sanitizer_common/sanitizer_mac.cc
===================================================================
--- lib/sanitizer_common/sanitizer_mac.cc
+++ lib/sanitizer_common/sanitizer_mac.cc
@@ -414,10 +414,7 @@
   memory_mapping.DumpListOfModules(&modules_);
 }
 
-HandleSignalMode GetHandleSignalMode(int signum) {
-  // Handling fatal signals on watchOS and tvOS devices is disallowed.
-  if ((SANITIZER_WATCHOS || SANITIZER_TVOS) && !(SANITIZER_IOSSIM))
-    return kHandleSignalNo;
+static HandleSignalMode GetHandleSignalModeImpl(int signum) {
   switch (signum) {
     case SIGABRT:
       return common_flags()->handle_abort;
@@ -433,6 +430,16 @@
   return kHandleSignalNo;
 }
 
+HandleSignalMode GetHandleSignalMode(int signum) {
+  // Handling fatal signals on watchOS and tvOS devices is disallowed.
+  if ((SANITIZER_WATCHOS || SANITIZER_TVOS) && !(SANITIZER_IOSSIM))
+    return kHandleSignalNo;
+  HandleSignalMode result = GetHandleSignalModeImpl(signum);
+  if (result == kHandleSignalYes && !common_flags()->allow_user_segv_handler)
+    return kHandleSignalExclusive;
+  return result;
+}
+
 MacosVersion cached_macos_version = MACOS_VERSION_UNINITIALIZED;
 
 MacosVersion GetMacosVersionInternal() {
Index: lib/sanitizer_common/sanitizer_linux.cc
===================================================================
--- lib/sanitizer_common/sanitizer_linux.cc
+++ lib/sanitizer_common/sanitizer_linux.cc
@@ -1396,7 +1396,7 @@
 
 #endif
 
-HandleSignalMode GetHandleSignalMode(int signum) {
+static HandleSignalMode GetHandleSignalModeImpl(int signum) {
   switch (signum) {
     case SIGABRT:
       return common_flags()->handle_abort;
@@ -1412,6 +1412,13 @@
   return kHandleSignalNo;
 }
 
+HandleSignalMode GetHandleSignalMode(int signum) {
+  HandleSignalMode result = GetHandleSignalModeImpl(signum);
+  if (result == kHandleSignalYes && !common_flags()->allow_user_segv_handler)
+    return kHandleSignalExclusive;
+  return result;
+}
+
 #if !SANITIZER_GO
 void *internal_start_thread(void(*func)(void *arg), void *arg) {
   // Start the thread with signals blocked, otherwise it can steal user signals.
Index: lib/sanitizer_common/sanitizer_flags.inc
===================================================================
--- lib/sanitizer_common/sanitizer_flags.inc
+++ lib/sanitizer_common/sanitizer_flags.inc
@@ -93,6 +93,9 @@
 COMMON_FLAG(HandleSignalMode, handle_sigfpe, kHandleSignalYes,
             COMMON_FLAG_HANDLE_SIGNAL_HELP(SIGFPE))
 #undef COMMON_FLAG_HANDLE_SIGNAL_HELP
+COMMON_FLAG(bool, allow_user_segv_handler, true,
+            "Deprecated. Thue has no effect, see handle_sigbus. If false, "
+            "handle_*=1 will be upgraded to handle_*=2.")
 COMMON_FLAG(bool, use_sigaltstack, true,
             "If set, uses alternate stack for signal handling.")
 COMMON_FLAG(bool, detect_deadlocks, false,


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