Fix -fsanitize=vptr badness in <__debug>

Summary:

This patch fixes a lifetime bug when inserting a new container into the debug database. It is
diagnosed by UBSAN when debug mode is enabled. This patch corrects how nodes are constructed
during insertion.

The fix requires unconditionally breaking the debug mode ABI. Users should not expect ABI
stability from debug mode.

Reviewers: ldionne, serge-sans-paille, EricWF

Reviewed By: EricWF

Subscribers: mclow.lists, christof, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D58011

llvm-svn: 355367

libcxx/include/__debug

@@ -250,16 +250,22 @@ public:
     __db_c_const_iterator __c_end() const;
     __db_i_const_iterator __i_end() const;
 
+    typedef __c_node*(_InsertConstruct)(void*, void*, __c_node*);
+
+    template <class _Cont>
+    _LIBCPP_INLINE_VISIBILITY static __c_node* __create_C_node(void *__mem, void *__c, __c_node *__next) {
+        return ::new(__mem) _C_node<_Cont>(__c, __next);
+    }
+
     template <class _Cont>
     _LIBCPP_INLINE_VISIBILITY
     void __insert_c(_Cont* __c)
     {
-        __c_node* __n = __insert_c(static_cast<void*>(__c));
-        ::new(__n) _C_node<_Cont>(__n->__c_, __n->__next_);
+        __insert_c(static_cast<void*>(__c), &__create_C_node<_Cont>);
     }
 
     void __insert_i(void* __i);
-    __c_node* __insert_c(void* __c);
+    void __insert_c(void* __c, _InsertConstruct* __fn);
     void __erase_c(void* __c);
 
     void __insert_ic(void* __i, const void* __c);

libcxx/lib/abi/CHANGELOG.TXT

@@ -12,6 +12,32 @@ Afterwards the ABI list should be updated to include the new changes.
 
 New entries should be added directly below the "Version" header.
 
+-----------
+Version 9.0
+-----------
+
+* rTBD - Fix -fsanitize=vptr badness in <__debug>
+
+  This patch fixes a lifetime bug when inserting a new container into the debug database. It is
+  diagnosed by UBSAN when debug mode is enabled. This patch corrects how nodes are constructed
+  during insertion.
+
+  The fix requires unconditionally breaking the debug mode ABI. Users should not expect ABI
+  stability from debug mode.
+
+
+  x86_64-unknown-linux-gnu
+  ------------------------
+  Symbol added: _ZNSt3__111__libcpp_db10__insert_cEPvPFPNS_8__c_nodeES1_S1_S3_E
+  Symbol removed: _ZNSt3__111__libcpp_db10__insert_cEPv
+
+
+  x86_64-apple-apple-darwin
+  -------------------------
+  Symbol added: __ZNSt3__111__libcpp_db10__insert_cEPvPFPNS_8__c_nodeES1_S1_S3_E
+  Symbol removed: __ZNSt3__111__libcpp_db10__insert_cEPv
+
+
 -----------
 Version 8.0
 -----------

libcxx/lib/abi/x86_64-apple-darwin.v1.abilist

@@ -599,7 +599,7 @@
 {'is_defined': True, 'name': '__ZNSt3__110to_wstringEx', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__110to_wstringEy', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__111__call_onceERVmPvPFvS2_E', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__111__libcpp_db10__insert_cEPv', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__111__libcpp_db10__insert_cEPvPFPNS_8__c_nodeES1_S1_S3_E', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__111__libcpp_db10__insert_iEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__111__libcpp_db11__insert_icEPvPKv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__111__libcpp_db15__iterator_copyEPvPKv', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-apple-darwin.v2.abilist

@@ -602,7 +602,7 @@
 {'is_defined': True, 'name': '__ZNSt3__210to_wstringEx', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__210to_wstringEy', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__211__call_onceERVmPvPFvS2_E', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__211__libcpp_db10__insert_cEPv', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__211__libcpp_db10__insert_cEPvPFPNS_8__c_nodeES1_S1_S3_E', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__211__libcpp_db10__insert_iEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__211__libcpp_db11__insert_icEPvPKv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__211__libcpp_db15__iterator_copyEPvPKv', 'type': 'FUNC'}

libcxx/lib/abi/x86_64-unknown-linux-gnu.v1.abilist

@@ -512,7 +512,7 @@
 {'is_defined': True, 'name': '_ZNSt3__110to_wstringEx', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__110to_wstringEy', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__111__call_onceERVmPvPFvS2_E', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__111__libcpp_db10__insert_cEPv', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__111__libcpp_db10__insert_cEPvPFPNS_8__c_nodeES1_S1_S3_E', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__111__libcpp_db10__insert_iEPv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__111__libcpp_db11__insert_icEPvPKv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__111__libcpp_db15__iterator_copyEPvPKv', 'type': 'FUNC'}

libcxx/src/debug.cpp

@@ -203,8 +203,8 @@ __libcpp_db::__insert_ic(void* __i, const void* __c)
     i->__c_ = c;
 }
 
-__c_node*
-__libcpp_db::__insert_c(void* __c)
+void
+__libcpp_db::__insert_c(void* __c, __libcpp_db::_InsertConstruct *__fn)
 {
 #ifndef _LIBCPP_HAS_NO_THREADS
     WLock _(mut());
@@ -234,15 +234,12 @@ __libcpp_db::__insert_c(void* __c)
     }
     size_t hc = hash<void*>()(__c) % static_cast<size_t>(__cend_ - __cbeg_);
     __c_node* p = __cbeg_[hc];
-    __c_node* r = __cbeg_[hc] =
-      static_cast<__c_node*>(malloc(sizeof(__c_node)));
-    if (__cbeg_[hc] == nullptr)
-        __throw_bad_alloc();
+    void *buf = malloc(sizeof(__c_node));
+    if (buf == nullptr)
+      __throw_bad_alloc();
+    __cbeg_[hc] = __fn(buf, __c, p);
 
-    r->__c_ = __c;
-    r->__next_ = p;
     ++__csz_;
-    return r;
 }
 
 void

libcxx/test/libcxx/debug/containers/db_sequence_container_iterators.pass.cpp

@@ -40,6 +40,7 @@ public:
   static void run() {
     Base::run();
     try {
+      SanityTest();
       FrontOnEmptyContainer();
 
       if constexpr (CT != CT_ForwardList) {
@@ -71,6 +72,12 @@ public:
   }
 
 private:
+  static void SanityTest() {
+    CHECKPOINT("sanity test");
+    Container C = {1, 1, 1, 1};
+    ::DoNotOptimize(&C);
+  }
+
   static void RemoveFirstElem() {
     // See llvm.org/PR35564
     CHECKPOINT("remove(<first-elem>)");

libcxx/utils/libcxx/test/config.py

@@ -939,7 +939,7 @@ class Configuration(object):
 
             def add_ubsan():
                 self.cxx.flags += ['-fsanitize=undefined',
-                                   '-fno-sanitize=vptr,function,float-divide-by-zero',
+                                   '-fno-sanitize=float-divide-by-zero',
                                    '-fno-sanitize-recover=all']
                 self.exec_env['UBSAN_OPTIONS'] = 'print_stacktrace=1'
                 self.config.available_features.add('ubsan')