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 <assert.h>
8
9 #include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
10 #include "mojo/public/cpp/system/core.h"
11
12 namespace mojo {
13 namespace internal {
14
BoundsChecker(const void * data,uint32_t data_num_bytes,size_t num_handles)15 BoundsChecker::BoundsChecker(const void* data, uint32_t data_num_bytes,
16 size_t num_handles)
17 : data_begin_(reinterpret_cast<uintptr_t>(data)),
18 data_end_(data_begin_ + data_num_bytes),
19 handle_begin_(0),
20 handle_end_(static_cast<uint32_t>(num_handles)) {
21 if (data_end_ < data_begin_) {
22 // The calculation of |data_end_| overflowed.
23 // It shouldn't happen but if it does, set the range to empty so
24 // IsValidRange() and ClaimMemory() always fail.
25 assert(false); // Not reached.
26 data_end_ = data_begin_;
27 }
28 if (handle_end_ < num_handles) {
29 // Assigning |num_handles| to |handle_end_| overflowed.
30 // It shouldn't happen but if it does, set the handle index range to empty.
31 assert(false); // Not reached.
32 handle_end_ = 0;
33 }
34 }
35
~BoundsChecker()36 BoundsChecker::~BoundsChecker() {
37 }
38
ClaimMemory(const void * position,uint32_t num_bytes)39 bool BoundsChecker::ClaimMemory(const void* position, uint32_t num_bytes) {
40 uintptr_t begin = reinterpret_cast<uintptr_t>(position);
41 uintptr_t end = begin + num_bytes;
42
43 if (!InternalIsValidRange(begin, end))
44 return false;
45
46 data_begin_ = end;
47 return true;
48 }
49
ClaimHandle(const Handle & encoded_handle)50 bool BoundsChecker::ClaimHandle(const Handle& encoded_handle) {
51 uint32_t index = encoded_handle.value();
52 if (index == kEncodedInvalidHandleValue)
53 return true;
54
55 if (index < handle_begin_ || index >= handle_end_)
56 return false;
57
58 // |index| + 1 shouldn't overflow, because |index| is not the max value of
59 // uint32_t (it is less than |handle_end_|).
60 handle_begin_ = index + 1;
61 return true;
62 }
63
IsValidRange(const void * position,uint32_t num_bytes) const64 bool BoundsChecker::IsValidRange(const void* position,
65 uint32_t num_bytes) const {
66 uintptr_t begin = reinterpret_cast<uintptr_t>(position);
67 uintptr_t end = begin + num_bytes;
68
69 return InternalIsValidRange(begin, end);
70 }
71
InternalIsValidRange(uintptr_t begin,uintptr_t end) const72 bool BoundsChecker::InternalIsValidRange(uintptr_t begin, uintptr_t end) const {
73 return end > begin && begin >= data_begin_ && end <= data_end_;
74 }
75
76 } // namespace internal
77 } // namespace mojo
78