1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "mojo/public/cpp/bindings/lib/bounds_checker.h" 6 7 #include "mojo/public/cpp/bindings/lib/bindings_serialization.h" 8 #include "mojo/public/cpp/environment/logging.h" 9 #include "mojo/public/cpp/system/handle.h" 10 11 namespace mojo { 12 namespace internal { 13 14 BoundsChecker::BoundsChecker(const void* data, uint32_t data_num_bytes, 15 size_t num_handles) 16 : data_begin_(reinterpret_cast<uintptr_t>(data)), 17 data_end_(data_begin_ + data_num_bytes), 18 handle_begin_(0), 19 handle_end_(static_cast<uint32_t>(num_handles)) { 20 if (data_end_ < data_begin_) { 21 // The calculation of |data_end_| overflowed. 22 // It shouldn't happen but if it does, set the range to empty so 23 // IsValidRange() and ClaimMemory() always fail. 24 MOJO_DCHECK(false) << "Not reached"; 25 data_end_ = data_begin_; 26 } 27 if (handle_end_ < num_handles) { 28 // Assigning |num_handles| to |handle_end_| overflowed. 29 // It shouldn't happen but if it does, set the handle index range to empty. 30 MOJO_DCHECK(false) << "Not reached"; 31 handle_end_ = 0; 32 } 33 } 34 35 BoundsChecker::~BoundsChecker() { 36 } 37 38 bool BoundsChecker::ClaimMemory(const void* position, uint32_t num_bytes) { 39 uintptr_t begin = reinterpret_cast<uintptr_t>(position); 40 uintptr_t end = begin + num_bytes; 41 42 if (!InternalIsValidRange(begin, end)) 43 return false; 44 45 data_begin_ = end; 46 return true; 47 } 48 49 bool BoundsChecker::ClaimHandle(const Handle& encoded_handle) { 50 uint32_t index = encoded_handle.value(); 51 if (index == kEncodedInvalidHandleValue) 52 return true; 53 54 if (index < handle_begin_ || index >= handle_end_) 55 return false; 56 57 // |index| + 1 shouldn't overflow, because |index| is not the max value of 58 // uint32_t (it is less than |handle_end_|). 59 handle_begin_ = index + 1; 60 return true; 61 } 62 63 bool BoundsChecker::IsValidRange(const void* position, 64 uint32_t num_bytes) const { 65 uintptr_t begin = reinterpret_cast<uintptr_t>(position); 66 uintptr_t end = begin + num_bytes; 67 68 return InternalIsValidRange(begin, end); 69 } 70 71 bool BoundsChecker::InternalIsValidRange(uintptr_t begin, uintptr_t end) const { 72 return end > begin && begin >= data_begin_ && end <= data_end_; 73 } 74 75 } // namespace internal 76 } // namespace mojo 77
