1 // Copyright (c) 2011 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 "base/posix/file_descriptor_shuffle.h"
6
7 #include <unistd.h>
8 #include <stddef.h>
9 #include <ostream>
10
11 #include "base/posix/eintr_wrapper.h"
12 #include "base/logging.h"
13
14 namespace base {
15
PerformInjectiveMultimapDestructive(InjectiveMultimap * m,InjectionDelegate * delegate)16 bool PerformInjectiveMultimapDestructive(
17 InjectiveMultimap* m, InjectionDelegate* delegate) {
18 static const size_t kMaxExtraFDs = 16;
19 int extra_fds[kMaxExtraFDs];
20 unsigned next_extra_fd = 0;
21
22 // DANGER: this function must not allocate or lock.
23 // Cannot use STL iterators here, since debug iterators use locks.
24
25 for (size_t i_index = 0; i_index < m->size(); ++i_index) {
26 InjectiveMultimap::value_type* i = &(*m)[i_index];
27 int temp_fd = -1;
28
29 // We DCHECK the injectiveness of the mapping.
30 for (size_t j_index = i_index + 1; j_index < m->size(); ++j_index) {
31 InjectiveMultimap::value_type* j = &(*m)[j_index];
32 DCHECK(i->dest != j->dest) << "Both fd " << i->source
33 << " and " << j->source << " map to " << i->dest;
34 }
35
36 const bool is_identity = i->source == i->dest;
37
38 for (size_t j_index = i_index + 1; j_index < m->size(); ++j_index) {
39 InjectiveMultimap::value_type* j = &(*m)[j_index];
40 if (!is_identity && i->dest == j->source) {
41 if (temp_fd == -1) {
42 if (!delegate->Duplicate(&temp_fd, i->dest))
43 return false;
44 if (next_extra_fd < kMaxExtraFDs) {
45 extra_fds[next_extra_fd++] = temp_fd;
46 } else {
47 RAW_LOG(ERROR, "PerformInjectiveMultimapDestructive overflowed "
48 "extra_fds. Leaking file descriptors!");
49 }
50 }
51
52 j->source = temp_fd;
53 j->close = false;
54 }
55
56 if (i->close && i->source == j->dest)
57 i->close = false;
58
59 if (i->close && i->source == j->source) {
60 i->close = false;
61 j->close = true;
62 }
63 }
64
65 if (!is_identity) {
66 if (!delegate->Move(i->source, i->dest))
67 return false;
68 }
69
70 if (!is_identity && i->close)
71 delegate->Close(i->source);
72 }
73
74 for (unsigned i = 0; i < next_extra_fd; i++)
75 delegate->Close(extra_fds[i]);
76
77 return true;
78 }
79
PerformInjectiveMultimap(const InjectiveMultimap & m_in,InjectionDelegate * delegate)80 bool PerformInjectiveMultimap(const InjectiveMultimap& m_in,
81 InjectionDelegate* delegate) {
82 InjectiveMultimap m(m_in);
83 return PerformInjectiveMultimapDestructive(&m, delegate);
84 }
85
Duplicate(int * result,int fd)86 bool FileDescriptorTableInjection::Duplicate(int* result, int fd) {
87 *result = HANDLE_EINTR(dup(fd));
88 return *result >= 0;
89 }
90
Move(int src,int dest)91 bool FileDescriptorTableInjection::Move(int src, int dest) {
92 return HANDLE_EINTR(dup2(src, dest)) != -1;
93 }
94
Close(int fd)95 void FileDescriptorTableInjection::Close(int fd) {
96 int ret = IGNORE_EINTR(close(fd));
97 DPCHECK(ret == 0);
98 }
99
100 } // namespace base
101