Author: ericwf Date: Mon Nov 24 12:46:37 2014 New Revision: 222674 URL: http://llvm.org/viewvc/llvm-project?rev=222674&view=rev Log: [libcxxabi] Delay adjustment of pointer to prevent referencing invalid memory.
Summary: This patch delays the dereference adjustment until we are sure the thrown type is a pointer type. It is possible the thrown type is not a pointer and is smaller than `sizeof(void*)`. If the thrown type is is smaller than `sizeof(void*)` the deference adjustment will result in a heap buffer overflow. I audited all the call sites of `can_catch(...)` and there are no places where `adjustedPtr` is used if `can_catch(...)` returns false. For this reason the patch should not introduce any functionality change. This patch fixes the following tests when using ASAN: * unwind_01.cpp * unwind_02.cpp * unwind_04.cpp Reviewers: danalbert, jroelofs, mclow.lists Reviewed By: mclow.lists Subscribers: cfe-commits Differential Revision: http://reviews.llvm.org/D6353 Modified: libcxxabi/trunk/src/private_typeinfo.cpp Modified: libcxxabi/trunk/src/private_typeinfo.cpp URL: http://llvm.org/viewvc/llvm-project/libcxxabi/trunk/src/private_typeinfo.cpp?rev=222674&r1=222673&r2=222674&view=diff ============================================================================== --- libcxxabi/trunk/src/private_typeinfo.cpp (original) +++ libcxxabi/trunk/src/private_typeinfo.cpp Mon Nov 24 12:46:37 2014 @@ -347,30 +347,34 @@ bool __pbase_type_info::can_catch(const __shim_type_info* thrown_type, void*&) const { - if (is_equal(this, thrown_type, false)) - return true; - return is_equal(thrown_type, &typeid(std::nullptr_t), false); + return is_equal(this, thrown_type, false) || + is_equal(thrown_type, &typeid(std::nullptr_t), false); } #pragma clang diagnostic push #pragma clang diagnostic ignored "-Wmissing-field-initializers" // Handles bullets 1, 3 and 4 +// NOTE: It might not be safe to adjust the pointer if it is not not a pointer +// type. Only adjust the pointer after we know it is safe to do so. bool __pointer_type_info::can_catch(const __shim_type_info* thrown_type, void*& adjustedPtr) const { - // Do the dereference adjustment - if (adjustedPtr != NULL) - adjustedPtr = *static_cast<void**>(adjustedPtr); // bullets 1 and 4 - if (__pbase_type_info::can_catch(thrown_type, adjustedPtr)) + if (__pbase_type_info::can_catch(thrown_type, adjustedPtr)) { + if (adjustedPtr != NULL) + adjustedPtr = *static_cast<void**>(adjustedPtr); return true; + } // bullet 3 const __pointer_type_info* thrown_pointer_type = dynamic_cast<const __pointer_type_info*>(thrown_type); if (thrown_pointer_type == 0) return false; + // Do the dereference adjustment + if (adjustedPtr != NULL) + adjustedPtr = *static_cast<void**>(adjustedPtr); // bullet 3B if (thrown_pointer_type->__flags & ~__flags) return false; _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
