1 /*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specic language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "libappfuse/FuseBuffer.h"
18
19 #include <inttypes.h>
20 #include <string.h>
21 #include <unistd.h>
22
23 #include <algorithm>
24 #include <type_traits>
25
26 #include <sys/socket.h>
27 #include <sys/uio.h>
28
29 #include <android-base/file.h>
30 #include <android-base/logging.h>
31 #include <android-base/macros.h>
32
33 namespace android {
34 namespace fuse {
35 namespace {
36
37 constexpr useconds_t kRetrySleepForWriting = 1000; // 1 ms
38
39 template <typename T>
CheckHeaderLength(const FuseMessage<T> * self,const char * name,size_t max_size)40 bool CheckHeaderLength(const FuseMessage<T>* self, const char* name, size_t max_size) {
41 const auto& header = static_cast<const T*>(self)->header;
42 if (header.len >= sizeof(header) && header.len <= max_size) {
43 return true;
44 } else {
45 LOG(ERROR) << "Invalid header length is found in " << name << ": " << header.len;
46 return false;
47 }
48 }
49
50 template <typename T>
ReadInternal(FuseMessage<T> * self,int fd,int sockflag)51 ResultOrAgain ReadInternal(FuseMessage<T>* self, int fd, int sockflag) {
52 char* const buf = reinterpret_cast<char*>(self);
53 const ssize_t result = sockflag ? TEMP_FAILURE_RETRY(recv(fd, buf, sizeof(T), sockflag))
54 : TEMP_FAILURE_RETRY(read(fd, buf, sizeof(T)));
55
56 switch (result) {
57 case 0:
58 // Expected EOF.
59 return ResultOrAgain::kFailure;
60 case -1:
61 if (errno == EAGAIN) {
62 return ResultOrAgain::kAgain;
63 }
64 PLOG(ERROR) << "Failed to read a FUSE message";
65 return ResultOrAgain::kFailure;
66 }
67
68 const auto& header = static_cast<const T*>(self)->header;
69 if (result < static_cast<ssize_t>(sizeof(header))) {
70 LOG(ERROR) << "Read bytes " << result << " are shorter than header size " << sizeof(header);
71 return ResultOrAgain::kFailure;
72 }
73
74 if (!CheckHeaderLength<T>(self, "Read", sizeof(T))) {
75 return ResultOrAgain::kFailure;
76 }
77
78 if (static_cast<uint32_t>(result) != header.len) {
79 LOG(ERROR) << "Read bytes " << result << " are different from header.len " << header.len;
80 return ResultOrAgain::kFailure;
81 }
82
83 return ResultOrAgain::kSuccess;
84 }
85
86 template <typename T>
WriteInternal(const FuseMessage<T> * self,int fd,int sockflag,const void * data,size_t max_size)87 ResultOrAgain WriteInternal(const FuseMessage<T>* self, int fd, int sockflag, const void* data,
88 size_t max_size) {
89 if (!CheckHeaderLength<T>(self, "Write", max_size)) {
90 return ResultOrAgain::kFailure;
91 }
92
93 const char* const buf = reinterpret_cast<const char*>(self);
94 const auto& header = static_cast<const T*>(self)->header;
95
96 while (true) {
97 int result;
98 if (sockflag) {
99 CHECK(data == nullptr);
100 result = TEMP_FAILURE_RETRY(send(fd, buf, header.len, sockflag));
101 } else if (data) {
102 const struct iovec vec[] = {{const_cast<char*>(buf), sizeof(header)},
103 {const_cast<void*>(data), header.len - sizeof(header)}};
104 result = TEMP_FAILURE_RETRY(writev(fd, vec, arraysize(vec)));
105 } else {
106 result = TEMP_FAILURE_RETRY(write(fd, buf, header.len));
107 }
108 if (result == -1) {
109 switch (errno) {
110 case ENOBUFS:
111 // When returning ENOBUFS, epoll still reports the FD is writable. Just usleep
112 // and retry again.
113 usleep(kRetrySleepForWriting);
114 continue;
115 case EAGAIN:
116 return ResultOrAgain::kAgain;
117 default:
118 PLOG(ERROR) << "Failed to write a FUSE message";
119 return ResultOrAgain::kFailure;
120 }
121 }
122
123 if (static_cast<unsigned int>(result) != header.len) {
124 LOG(ERROR) << "Written bytes " << result << " is different from length in header "
125 << header.len;
126 return ResultOrAgain::kFailure;
127 }
128 return ResultOrAgain::kSuccess;
129 }
130 }
131 }
132
133 static_assert(std::is_standard_layout<FuseBuffer>::value,
134 "FuseBuffer must be standard layout union.");
135
SetupMessageSockets(base::unique_fd (* result)[2])136 bool SetupMessageSockets(base::unique_fd (*result)[2]) {
137 base::unique_fd fds[2];
138 {
139 int raw_fds[2];
140 if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_fds) == -1) {
141 PLOG(ERROR) << "Failed to create sockets for proxy";
142 return false;
143 }
144 fds[0].reset(raw_fds[0]);
145 fds[1].reset(raw_fds[1]);
146 }
147
148 constexpr int kMaxMessageSize = sizeof(FuseBuffer);
149 if (setsockopt(fds[0], SOL_SOCKET, SO_SNDBUFFORCE, &kMaxMessageSize, sizeof(int)) != 0 ||
150 setsockopt(fds[1], SOL_SOCKET, SO_SNDBUFFORCE, &kMaxMessageSize, sizeof(int)) != 0) {
151 PLOG(ERROR) << "Failed to update buffer size for socket";
152 return false;
153 }
154
155 (*result)[0] = std::move(fds[0]);
156 (*result)[1] = std::move(fds[1]);
157 return true;
158 }
159
160 template <typename T>
Read(int fd)161 bool FuseMessage<T>::Read(int fd) {
162 return ReadInternal(this, fd, 0) == ResultOrAgain::kSuccess;
163 }
164
165 template <typename T>
ReadOrAgain(int fd)166 ResultOrAgain FuseMessage<T>::ReadOrAgain(int fd) {
167 return ReadInternal(this, fd, MSG_DONTWAIT);
168 }
169
170 template <typename T>
Write(int fd) const171 bool FuseMessage<T>::Write(int fd) const {
172 return WriteInternal(this, fd, 0, nullptr, sizeof(T)) == ResultOrAgain::kSuccess;
173 }
174
175 template <typename T>
WriteWithBody(int fd,size_t max_size,const void * data) const176 bool FuseMessage<T>::WriteWithBody(int fd, size_t max_size, const void* data) const {
177 CHECK(data != nullptr);
178 return WriteInternal(this, fd, 0, data, max_size) == ResultOrAgain::kSuccess;
179 }
180
181 template <typename T>
WriteOrAgain(int fd) const182 ResultOrAgain FuseMessage<T>::WriteOrAgain(int fd) const {
183 return WriteInternal(this, fd, MSG_DONTWAIT, nullptr, sizeof(T));
184 }
185
Reset(uint32_t data_length,uint32_t opcode,uint64_t unique)186 void FuseRequest::Reset(
187 uint32_t data_length, uint32_t opcode, uint64_t unique) {
188 memset(this, 0, sizeof(fuse_in_header) + data_length);
189 header.len = sizeof(fuse_in_header) + data_length;
190 header.opcode = opcode;
191 header.unique = unique;
192 }
193
194 template <size_t N>
ResetHeader(uint32_t data_length,int32_t error,uint64_t unique)195 void FuseResponseBase<N>::ResetHeader(uint32_t data_length, int32_t error, uint64_t unique) {
196 CHECK_LE(error, 0) << "error should be zero or negative.";
197 header.len = sizeof(fuse_out_header) + data_length;
198 header.error = error;
199 header.unique = unique;
200 }
201
202 template <size_t N>
Reset(uint32_t data_length,int32_t error,uint64_t unique)203 void FuseResponseBase<N>::Reset(uint32_t data_length, int32_t error, uint64_t unique) {
204 memset(this, 0, sizeof(fuse_out_header) + data_length);
205 ResetHeader(data_length, error, unique);
206 }
207
HandleInit()208 void FuseBuffer::HandleInit() {
209 const fuse_init_in* const in = &request.init_in;
210
211 // Before writing |out|, we need to copy data from |in|.
212 const uint64_t unique = request.header.unique;
213 const uint32_t minor = in->minor;
214 const uint32_t max_readahead = in->max_readahead;
215
216 // Kernel 2.6.16 is the first stable kernel with struct fuse_init_out
217 // defined (fuse version 7.6). The structure is the same from 7.6 through
218 // 7.22. Beginning with 7.23, the structure increased in size and added
219 // new parameters.
220 if (in->major != FUSE_KERNEL_VERSION || in->minor < 6) {
221 LOG(ERROR) << "Fuse kernel version mismatch: Kernel version " << in->major
222 << "." << in->minor << " Expected at least " << FUSE_KERNEL_VERSION
223 << ".6";
224 response.Reset(0, -EPERM, unique);
225 return;
226 }
227
228 // We limit ourselves to minor=15 because we don't handle BATCH_FORGET yet.
229 // Thus we need to use FUSE_COMPAT_22_INIT_OUT_SIZE.
230 #if defined(FUSE_COMPAT_22_INIT_OUT_SIZE)
231 // FUSE_KERNEL_VERSION >= 23.
232 const size_t response_size = FUSE_COMPAT_22_INIT_OUT_SIZE;
233 #else
234 const size_t response_size = sizeof(fuse_init_out);
235 #endif
236
237 response.Reset(response_size, kFuseSuccess, unique);
238 fuse_init_out* const out = &response.init_out;
239 out->major = FUSE_KERNEL_VERSION;
240 out->minor = std::min(minor, 15u);
241 out->max_readahead = max_readahead;
242 out->flags = FUSE_ATOMIC_O_TRUNC | FUSE_BIG_WRITES;
243 out->max_background = 32;
244 out->congestion_threshold = 32;
245 out->max_write = kFuseMaxWrite;
246 }
247
HandleNotImpl()248 void FuseBuffer::HandleNotImpl() {
249 LOG(VERBOSE) << "NOTIMPL op=" << request.header.opcode << " uniq="
250 << request.header.unique << " nid=" << request.header.nodeid;
251 const uint64_t unique = request.header.unique;
252 response.Reset(0, -ENOSYS, unique);
253 }
254
255 template class FuseMessage<FuseRequest>;
256 template class FuseMessage<FuseResponse>;
257 template class FuseMessage<FuseSimpleResponse>;
258 template struct FuseResponseBase<0u>;
259 template struct FuseResponseBase<kFuseMaxRead>;
260
261 } // namespace fuse
262 } // namespace android
263