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shared_ptr<bool> vptr_deleter_armed_flag_ptr (instead of unique_ptr) (#2882)

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* shared_ptr<bool> vptr_deleter_armed_flag_ptr (instead of unique_ptr), to fix heap-use-after-free bug.

* Fixing  generated by some compilers in the pybind11 CI suite.
This commit is contained in:
Ralf W. Grosse-Kunstleve 2021-03-02 17:43:25 -08:00 committed by GitHub
parent 6285177afe
commit 3a336a2047
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 40 additions and 13 deletions
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32
include/pybind11/detail/smart_holder_poc.h
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@ -38,10 +38,8 @@ Details:
* If created from an external `shared_ptr`, or a `unique_ptr` with a custom
deleter, including life-time management for external objects is infeasible.
* The smart_holder is movable but not copyable, as a consequence of using
unique_ptr for the vptr_deleter_armed_flag_ptr. Note that the bool for
the flag has to live on the heap, for the smart_holder to be movable.
unique_ptr is a great fit for this situation.
* By choice, the smart_holder is movable but not copyable, to keep the design
simple, and to guard against accidental copying overhead.
*/
#pragma once
@ -60,8 +58,9 @@ namespace memory {
template <typename T>
struct guarded_builtin_delete {
bool *flag_ptr;
explicit guarded_builtin_delete(bool *armed_flag_ptr) : flag_ptr{armed_flag_ptr} {}
std::shared_ptr<bool> flag_ptr;
explicit guarded_builtin_delete(std::shared_ptr<bool> armed_flag_ptr)
: flag_ptr{armed_flag_ptr} {}
template <typename T_ = T,
typename std::enable_if<std::is_destructible<T_>::value, int>::type = 0>
void operator()(T *raw_ptr) {
@ -80,8 +79,9 @@ struct guarded_builtin_delete {
template <typename T, typename D>
struct guarded_custom_deleter {
bool *flag_ptr;
explicit guarded_custom_deleter(bool *armed_flag_ptr) : flag_ptr{armed_flag_ptr} {}
std::shared_ptr<bool> flag_ptr;
explicit guarded_custom_deleter(std::shared_ptr<bool> armed_flag_ptr)
: flag_ptr{armed_flag_ptr} {}
void operator()(T *raw_ptr) {
if (*flag_ptr)
D()(raw_ptr);
@ -96,13 +96,19 @@ inline bool is_std_default_delete(const std::type_info &rtti_deleter) {
struct smart_holder {
const std::type_info *rtti_uqp_del;
std::unique_ptr<bool> vptr_deleter_armed_flag_ptr;
std::shared_ptr<bool> vptr_deleter_armed_flag_ptr;
std::shared_ptr<void> vptr;
bool vptr_is_using_noop_deleter : 1;
bool vptr_is_using_builtin_delete : 1;
bool vptr_is_external_shared_ptr : 1;
bool is_populated : 1;
// Design choice: smart_holder is movable but not copyable.
smart_holder(smart_holder &&) = default;
smart_holder(const smart_holder &) = delete;
smart_holder &operator=(smart_holder &&) = default;
smart_holder &operator=(const smart_holder &) = delete;
smart_holder()
: rtti_uqp_del{nullptr}, vptr_is_using_noop_deleter{false},
vptr_is_using_builtin_delete{false}, vptr_is_external_shared_ptr{false}, is_populated{
@ -182,7 +188,7 @@ struct smart_holder {
template <typename T>
static smart_holder from_raw_ptr_unowned(T *raw_ptr) {
smart_holder hld(false);
hld.vptr.reset(raw_ptr, guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr.get()));
hld.vptr.reset(raw_ptr, guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr));
hld.vptr_is_using_noop_deleter = true;
hld.is_populated = true;
return hld;
@ -213,7 +219,7 @@ struct smart_holder {
static smart_holder from_raw_ptr_take_ownership(T *raw_ptr) {
ensure_pointee_is_destructible<T>("from_raw_ptr_take_ownership");
smart_holder hld(true);
hld.vptr.reset(raw_ptr, guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr.get()));
hld.vptr.reset(raw_ptr, guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr));
hld.vptr_is_using_builtin_delete = true;
hld.is_populated = true;
return hld;
@ -246,10 +252,10 @@ struct smart_holder {
hld.vptr_is_using_builtin_delete = is_std_default_delete<T>(*hld.rtti_uqp_del);
if (hld.vptr_is_using_builtin_delete) {
hld.vptr.reset(unq_ptr.get(),
guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr.get()));
guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr));
} else {
hld.vptr.reset(unq_ptr.get(),
guarded_custom_deleter<T, D>(hld.vptr_deleter_armed_flag_ptr.get()));
guarded_custom_deleter<T, D>(hld.vptr_deleter_armed_flag_ptr));
}
unq_ptr.release();
hld.is_populated = true;

21
tests/pure_cpp/smart_holder_poc_test.cpp
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@ -302,3 +302,24 @@ TEST_CASE("indestructible_int-from_raw_ptr_take_ownership", "[E]") {
REQUIRE_THROWS_WITH(smart_holder::from_raw_ptr_take_ownership(value),
"Pointee is not destructible (from_raw_ptr_take_ownership).");
}
TEST_CASE("from_raw_ptr_take_ownership+as_shared_ptr-outliving_smart_holder", "[S]") {
// Exercises guarded_builtin_delete flag_ptr validity past destruction of smart_holder.
std::shared_ptr<int> longer_living;
{
auto hld = smart_holder::from_raw_ptr_take_ownership(new int(19));
longer_living = hld.as_shared_ptr<int>();
}
REQUIRE(*longer_living == 19);
}
TEST_CASE("from_unique_ptr_with_deleter+as_shared_ptr-outliving_smart_holder", "[S]") {
// Exercises guarded_custom_deleter flag_ptr validity past destruction of smart_holder.
std::shared_ptr<int> longer_living;
{
std::unique_ptr<int, helpers::functor_builtin_delete<int>> orig_owner(new int(19));
auto hld = smart_holder::from_unique_ptr(std::move(orig_owner));
longer_living = hld.as_shared_ptr<int>();
}
REQUIRE(*longer_living == 19);
}