[libc++] Fix use-after-free when building with _LIBCPP_DEBUG=1
The issue is the following code:
__cn1->__add(*__ip);
(*__ip)->__c_ = __cn1;
`__ip` points into the array of iterators for container `__cn2`. This code adds
the iterator to the array of iterators for `__cn1`, and updates the iterator to
point to the new container.
This code works fine, except when `__cn1` and `__cn2` are the same container.
`__cn1->__add()` might need to grow the array of iterators, and when it does,
`__ip` becomes invalid, so the second line becomes a use-after-free error.
Simply swapping the order of the above two lines is not sufficient, because of
the memmove() below. The easiest and most performant solution is just to skip
touching any iterators if the containers are the same.
Differential Revision: https://reviews.llvm.org/D58926
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@355550 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/list b/include/list
index 2afe2a2..7b59a0e 100644
--- a/include/list
+++ b/include/list
@@ -2013,22 +2013,24 @@
base::__sz() += __c.__sz();
__c.__sz() = 0;
#if _LIBCPP_DEBUG_LEVEL >= 2
- __libcpp_db* __db = __get_db();
- __c_node* __cn1 = __db->__find_c_and_lock(this);
- __c_node* __cn2 = __db->__find_c(&__c);
- for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
- {
- --__ip;
- iterator* __i = static_cast<iterator*>((*__ip)->__i_);
- if (__i->__ptr_ != __c.__end_as_link())
+ if (&__c != this) {
+ __libcpp_db* __db = __get_db();
+ __c_node* __cn1 = __db->__find_c_and_lock(this);
+ __c_node* __cn2 = __db->__find_c(&__c);
+ for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
{
- __cn1->__add(*__ip);
- (*__ip)->__c_ = __cn1;
- if (--__cn2->end_ != __ip)
- memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+ --__ip;
+ iterator* __i = static_cast<iterator*>((*__ip)->__i_);
+ if (__i->__ptr_ != __c.__end_as_link())
+ {
+ __cn1->__add(*__ip);
+ (*__ip)->__c_ = __cn1;
+ if (--__cn2->end_ != __ip)
+ memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+ }
}
+ __db->unlock();
}
- __db->unlock();
#endif
}
}
@@ -2056,22 +2058,24 @@
--__c.__sz();
++base::__sz();
#if _LIBCPP_DEBUG_LEVEL >= 2
- __libcpp_db* __db = __get_db();
- __c_node* __cn1 = __db->__find_c_and_lock(this);
- __c_node* __cn2 = __db->__find_c(&__c);
- for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
- {
- --__ip;
- iterator* __j = static_cast<iterator*>((*__ip)->__i_);
- if (__j->__ptr_ == __f)
+ if (&__c != this) {
+ __libcpp_db* __db = __get_db();
+ __c_node* __cn1 = __db->__find_c_and_lock(this);
+ __c_node* __cn2 = __db->__find_c(&__c);
+ for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
{
- __cn1->__add(*__ip);
- (*__ip)->__c_ = __cn1;
- if (--__cn2->end_ != __ip)
- memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+ --__ip;
+ iterator* __j = static_cast<iterator*>((*__ip)->__i_);
+ if (__j->__ptr_ == __f)
+ {
+ __cn1->__add(*__ip);
+ (*__ip)->__c_ = __cn1;
+ if (--__cn2->end_ != __ip)
+ memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+ }
}
+ __db->unlock();
}
- __db->unlock();
#endif
}
}
@@ -2110,26 +2114,28 @@
base::__unlink_nodes(__first, __last);
__link_nodes(__p.__ptr_, __first, __last);
#if _LIBCPP_DEBUG_LEVEL >= 2
- __libcpp_db* __db = __get_db();
- __c_node* __cn1 = __db->__find_c_and_lock(this);
- __c_node* __cn2 = __db->__find_c(&__c);
- for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
- {
- --__ip;
- iterator* __j = static_cast<iterator*>((*__ip)->__i_);
- for (__link_pointer __k = __f.__ptr_;
- __k != __l.__ptr_; __k = __k->__next_)
+ if (&__c != this) {
+ __libcpp_db* __db = __get_db();
+ __c_node* __cn1 = __db->__find_c_and_lock(this);
+ __c_node* __cn2 = __db->__find_c(&__c);
+ for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
{
- if (__j->__ptr_ == __k)
+ --__ip;
+ iterator* __j = static_cast<iterator*>((*__ip)->__i_);
+ for (__link_pointer __k = __f.__ptr_;
+ __k != __l.__ptr_; __k = __k->__next_)
{
- __cn1->__add(*__ip);
- (*__ip)->__c_ = __cn1;
- if (--__cn2->end_ != __ip)
- memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+ if (__j->__ptr_ == __k)
+ {
+ __cn1->__add(*__ip);
+ (*__ip)->__c_ = __cn1;
+ if (--__cn2->end_ != __ip)
+ memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
+ }
}
}
+ __db->unlock();
}
- __db->unlock();
#endif
}
}
diff --git a/test/libcxx/debug/containers/db_sequence_container_iterators.pass.cpp b/test/libcxx/debug/containers/db_sequence_container_iterators.pass.cpp
index 6ead98e..2de4c02 100644
--- a/test/libcxx/debug/containers/db_sequence_container_iterators.pass.cpp
+++ b/test/libcxx/debug/containers/db_sequence_container_iterators.pass.cpp
@@ -65,6 +65,7 @@
}
if constexpr (CT == CT_List) {
SpliceFirstElem();
+ SpliceSameContainer();
}
} catch (...) {
assert(false && "uncaught debug exception");
@@ -110,6 +111,11 @@
}
}
+ static void SpliceSameContainer() {
+ CHECKPOINT("splice(<same-container>)");
+ Container C = {1, 1};
+ C.splice(C.end(), C, C.begin());
+ }
static void SpliceFirstElemAfter() {
// See llvm.org/PR35564
