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 << "fd=" << fd << " "
120 << "sockflag=" << sockflag << " "
121 << "data=" << data;
122 return ResultOrAgain::kFailure;
123 }
124 }
125
126 if (static_cast<unsigned int>(result) != header.len) {
127 LOG(ERROR) << "Written bytes " << result << " is different from length in header "
128 << header.len;
129 return ResultOrAgain::kFailure;
130 }
131 return ResultOrAgain::kSuccess;
132 }
133 }
134 }
135
136 static_assert(std::is_standard_layout<FuseBuffer>::value,
137 "FuseBuffer must be standard layout union.");
138
SetupMessageSockets(base::unique_fd (* result)[2])139 bool SetupMessageSockets(base::unique_fd (*result)[2]) {
140 base::unique_fd fds[2];
141 {
142 int raw_fds[2];
143 if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_fds) == -1) {
144 PLOG(ERROR) << "Failed to create sockets for proxy";
145 return false;
146 }
147 fds[0].reset(raw_fds[0]);
148 fds[1].reset(raw_fds[1]);
149 }
150
151 constexpr int kMaxMessageSize = sizeof(FuseBuffer);
152 if (setsockopt(fds[0], SOL_SOCKET, SO_SNDBUF, &kMaxMessageSize, sizeof(int)) != 0 ||
153 setsockopt(fds[1], SOL_SOCKET, SO_SNDBUF, &kMaxMessageSize, sizeof(int)) != 0) {
154 PLOG(ERROR) << "Failed to update buffer size for socket";
155 return false;
156 }
157
158 (*result)[0] = std::move(fds[0]);
159 (*result)[1] = std::move(fds[1]);
160 return true;
161 }
162
163 template <typename T>
Read(int fd)164 bool FuseMessage<T>::Read(int fd) {
165 return ReadInternal(this, fd, 0) == ResultOrAgain::kSuccess;
166 }
167
168 template <typename T>
ReadOrAgain(int fd)169 ResultOrAgain FuseMessage<T>::ReadOrAgain(int fd) {
170 return ReadInternal(this, fd, MSG_DONTWAIT);
171 }
172
173 template <typename T>
Write(int fd) const174 bool FuseMessage<T>::Write(int fd) const {
175 return WriteInternal(this, fd, 0, nullptr, sizeof(T)) == ResultOrAgain::kSuccess;
176 }
177
178 template <typename T>
WriteWithBody(int fd,size_t max_size,const void * data) const179 bool FuseMessage<T>::WriteWithBody(int fd, size_t max_size, const void* data) const {
180 CHECK(data != nullptr);
181 return WriteInternal(this, fd, 0, data, max_size) == ResultOrAgain::kSuccess;
182 }
183
184 template <typename T>
WriteOrAgain(int fd) const185 ResultOrAgain FuseMessage<T>::WriteOrAgain(int fd) const {
186 return WriteInternal(this, fd, MSG_DONTWAIT, nullptr, sizeof(T));
187 }
188
Reset(uint32_t data_length,uint32_t opcode,uint64_t unique)189 void FuseRequest::Reset(
190 uint32_t data_length, uint32_t opcode, uint64_t unique) {
191 memset(this, 0, sizeof(fuse_in_header) + data_length);
192 header.len = sizeof(fuse_in_header) + data_length;
193 header.opcode = opcode;
194 header.unique = unique;
195 }
196
197 template <size_t N>
ResetHeader(uint32_t data_length,int32_t error,uint64_t unique)198 void FuseResponseBase<N>::ResetHeader(uint32_t data_length, int32_t error, uint64_t unique) {
199 CHECK_LE(error, 0) << "error should be zero or negative.";
200 header.len = sizeof(fuse_out_header) + data_length;
201 header.error = error;
202 header.unique = unique;
203 }
204
205 template <size_t N>
Reset(uint32_t data_length,int32_t error,uint64_t unique)206 void FuseResponseBase<N>::Reset(uint32_t data_length, int32_t error, uint64_t unique) {
207 memset(this, 0, sizeof(fuse_out_header) + data_length);
208 ResetHeader(data_length, error, unique);
209 }
210
HandleInit()211 void FuseBuffer::HandleInit() {
212 const fuse_init_in* const in = &request.init_in;
213
214 // Before writing |out|, we need to copy data from |in|.
215 const uint64_t unique = request.header.unique;
216 const uint32_t minor = in->minor;
217 const uint32_t max_readahead = in->max_readahead;
218
219 // Kernel 2.6.16 is the first stable kernel with struct fuse_init_out
220 // defined (fuse version 7.6). The structure is the same from 7.6 through
221 // 7.22. Beginning with 7.23, the structure increased in size and added
222 // new parameters.
223 if (in->major != FUSE_KERNEL_VERSION || in->minor < 6) {
224 LOG(ERROR) << "Fuse kernel version mismatch: Kernel version " << in->major
225 << "." << in->minor << " Expected at least " << FUSE_KERNEL_VERSION
226 << ".6";
227 response.Reset(0, -EPERM, unique);
228 return;
229 }
230
231 // We limit ourselves to minor=15 because we don't handle BATCH_FORGET yet.
232 // Thus we need to use FUSE_COMPAT_22_INIT_OUT_SIZE.
233 #if defined(FUSE_COMPAT_22_INIT_OUT_SIZE)
234 // FUSE_KERNEL_VERSION >= 23.
235 const size_t response_size = FUSE_COMPAT_22_INIT_OUT_SIZE;
236 #else
237 const size_t response_size = sizeof(fuse_init_out);
238 #endif
239
240 response.Reset(response_size, kFuseSuccess, unique);
241 fuse_init_out* const out = &response.init_out;
242 out->major = FUSE_KERNEL_VERSION;
243 out->minor = std::min(minor, 15u);
244 out->max_readahead = max_readahead;
245 out->flags = FUSE_ATOMIC_O_TRUNC | FUSE_BIG_WRITES;
246 out->max_background = 32;
247 out->congestion_threshold = 32;
248 out->max_write = kFuseMaxWrite;
249 }
250
HandleNotImpl()251 void FuseBuffer::HandleNotImpl() {
252 LOG(VERBOSE) << "NOTIMPL op=" << request.header.opcode << " uniq="
253 << request.header.unique << " nid=" << request.header.nodeid;
254 // Add volatile as a workaround for compiler issue which removes the temporary
255 // variable.
256 const volatile uint64_t unique = request.header.unique;
257 response.Reset(0, -ENOSYS, unique);
258 }
259
260 template class FuseMessage<FuseRequest>;
261 template class FuseMessage<FuseResponse>;
262 template class FuseMessage<FuseSimpleResponse>;
263 template struct FuseResponseBase<0u>;
264 template struct FuseResponseBase<kFuseMaxRead>;
265
266 } // namespace fuse
267 } // namespace android
268