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/file_descriptor_shuffle.h"
6
7 #include <unistd.h>
8 #include <stddef.h>
9 #include <ostream>
10
11 #include "base/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 may not allocate.
23
24 for (InjectiveMultimap::iterator i = m->begin(); i != m->end(); ++i) {
25 int temp_fd = -1;
26
27 // We DCHECK the injectiveness of the mapping.
28 for (InjectiveMultimap::iterator j = i + 1; j != m->end(); ++j) {
29 DCHECK(i->dest != j->dest) << "Both fd " << i->source
30 << " and " << j->source << " map to " << i->dest;
31 }
32
33 const bool is_identity = i->source == i->dest;
34
35 for (InjectiveMultimap::iterator j = i + 1; j != m->end(); ++j) {
36 if (!is_identity && i->dest == j->source) {
37 if (temp_fd == -1) {
38 if (!delegate->Duplicate(&temp_fd, i->dest))
39 return false;
40 if (next_extra_fd < kMaxExtraFDs) {
41 extra_fds[next_extra_fd++] = temp_fd;
42 } else {
43 RAW_LOG(ERROR, "PerformInjectiveMultimapDestructive overflowed "
44 "extra_fds. Leaking file descriptors!");
45 }
46 }
47
48 j->source = temp_fd;
49 j->close = false;
50 }
51
52 if (i->close && i->source == j->dest)
53 i->close = false;
54
55 if (i->close && i->source == j->source) {
56 i->close = false;
57 j->close = true;
58 }
59 }
60
61 if (!is_identity) {
62 if (!delegate->Move(i->source, i->dest))
63 return false;
64 }
65
66 if (!is_identity && i->close)
67 delegate->Close(i->source);
68 }
69
70 for (unsigned i = 0; i < next_extra_fd; i++)
71 delegate->Close(extra_fds[i]);
72
73 return true;
74 }
75
PerformInjectiveMultimap(const InjectiveMultimap & m_in,InjectionDelegate * delegate)76 bool PerformInjectiveMultimap(const InjectiveMultimap& m_in,
77 InjectionDelegate* delegate) {
78 InjectiveMultimap m(m_in);
79 return PerformInjectiveMultimapDestructive(&m, delegate);
80 }
81
Duplicate(int * result,int fd)82 bool FileDescriptorTableInjection::Duplicate(int* result, int fd) {
83 *result = HANDLE_EINTR(dup(fd));
84 return *result >= 0;
85 }
86
Move(int src,int dest)87 bool FileDescriptorTableInjection::Move(int src, int dest) {
88 return HANDLE_EINTR(dup2(src, dest)) != -1;
89 }
90
Close(int fd)91 void FileDescriptorTableInjection::Close(int fd) {
92 int ret = HANDLE_EINTR(close(fd));
93 DPCHECK(ret == 0);
94 }
95
96 } // namespace base
97