1 /* 2 * 9p utilities 3 * 4 * Copyright IBM, Corp. 2017 5 * 6 * Authors: 7 * Greg Kurz <groug@kaod.org> 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 */ 12 13 #ifndef QEMU_9P_UTIL_H 14 #define QEMU_9P_UTIL_H 15 16 #include "qemu/error-report.h" 17 18 #ifdef O_PATH 19 #define O_PATH_9P_UTIL O_PATH 20 #else 21 #define O_PATH_9P_UTIL 0 22 #endif 23 24 #if !defined(CONFIG_LINUX) 25 26 /* 27 * Generates a Linux device number (a.k.a. dev_t) for given device major 28 * and minor numbers. 29 * 30 * To be more precise: it generates a device number in glibc's format 31 * (MMMM_Mmmm_mmmM_MMmm, 64 bits) actually, which is compatible with 32 * Linux's format (mmmM_MMmm, 32 bits), as described in <bits/sysmacros.h>. 33 */ 34 static inline uint64_t makedev_dotl(uint32_t dev_major, uint32_t dev_minor) 35 { 36 uint64_t dev; 37 38 // from glibc sysmacros.h: 39 dev = (((uint64_t) (dev_major & 0x00000fffu)) << 8); 40 dev |= (((uint64_t) (dev_major & 0xfffff000u)) << 32); 41 dev |= (((uint64_t) (dev_minor & 0x000000ffu)) << 0); 42 dev |= (((uint64_t) (dev_minor & 0xffffff00u)) << 12); 43 return dev; 44 } 45 46 #endif 47 48 /* 49 * Converts given device number from host's device number format to Linux 50 * device number format. As both the size of type dev_t and encoding of 51 * dev_t is system dependent, we have to convert them for Linux guests if 52 * host is not running Linux. 53 */ 54 static inline uint64_t host_dev_to_dotl_dev(dev_t dev) 55 { 56 #ifdef CONFIG_LINUX 57 return dev; 58 #else 59 return makedev_dotl(major(dev), minor(dev)); 60 #endif 61 } 62 63 /* Translates errno from host -> Linux if needed */ 64 static inline int errno_to_dotl(int err) { 65 #if defined(CONFIG_LINUX) 66 /* nothing to translate (Linux -> Linux) */ 67 #elif defined(CONFIG_DARWIN) 68 /* 69 * translation mandatory for macOS hosts 70 * 71 * FIXME: Only most important errnos translated here yet, this should be 72 * extended to as many errnos being translated as possible in future. 73 */ 74 if (err == ENAMETOOLONG) { 75 err = 36; /* ==ENAMETOOLONG on Linux */ 76 } else if (err == ENOTEMPTY) { 77 err = 39; /* ==ENOTEMPTY on Linux */ 78 } else if (err == ELOOP) { 79 err = 40; /* ==ELOOP on Linux */ 80 } else if (err == ENOATTR) { 81 err = 61; /* ==ENODATA on Linux */ 82 } else if (err == ENOTSUP) { 83 err = 95; /* ==EOPNOTSUPP on Linux */ 84 } else if (err == EOPNOTSUPP) { 85 err = 95; /* ==EOPNOTSUPP on Linux */ 86 } 87 #else 88 #error Missing errno translation to Linux for this host system 89 #endif 90 return err; 91 } 92 93 #ifdef CONFIG_DARWIN 94 #define qemu_fgetxattr(...) fgetxattr(__VA_ARGS__, 0, 0) 95 #else 96 #define qemu_fgetxattr fgetxattr 97 #endif 98 99 #define qemu_openat openat 100 #define qemu_fstat fstat 101 #define qemu_fstatat fstatat 102 #define qemu_mkdirat mkdirat 103 #define qemu_renameat renameat 104 #define qemu_utimensat utimensat 105 #define qemu_unlinkat unlinkat 106 #define qemu_futimens futimens 107 108 static inline void close_preserve_errno(int fd) 109 { 110 int serrno = errno; 111 close(fd); 112 errno = serrno; 113 } 114 115 /** 116 * close_if_special_file() - Close @fd if neither regular file nor directory. 117 * 118 * @fd: file descriptor of open file 119 * Return: 0 on regular file or directory, -1 otherwise 120 * 121 * CVE-2023-2861: Prohibit opening any special file directly on host 122 * (especially device files), as a compromised client could potentially gain 123 * access outside exported tree under certain, unsafe setups. We expect 124 * client to handle I/O on special files exclusively on guest side. 125 */ 126 static inline int close_if_special_file(int fd) 127 { 128 struct stat stbuf; 129 130 if (qemu_fstat(fd, &stbuf) < 0) { 131 close_preserve_errno(fd); 132 return -1; 133 } 134 if (!S_ISREG(stbuf.st_mode) && !S_ISDIR(stbuf.st_mode)) { 135 error_report_once( 136 "9p: broken or compromised client detected; attempt to open " 137 "special file (i.e. neither regular file, nor directory)" 138 ); 139 close(fd); 140 errno = ENXIO; 141 return -1; 142 } 143 144 return 0; 145 } 146 147 static inline int openat_dir(int dirfd, const char *name) 148 { 149 return qemu_openat(dirfd, name, 150 O_DIRECTORY | O_RDONLY | O_NOFOLLOW | O_PATH_9P_UTIL); 151 } 152 153 static inline int openat_file(int dirfd, const char *name, int flags, 154 mode_t mode) 155 { 156 int fd, serrno, ret; 157 158 #ifndef CONFIG_DARWIN 159 again: 160 #endif 161 fd = qemu_openat(dirfd, name, flags | O_NOFOLLOW | O_NOCTTY | O_NONBLOCK, 162 mode); 163 if (fd == -1) { 164 #ifndef CONFIG_DARWIN 165 if (errno == EPERM && (flags & O_NOATIME)) { 166 /* 167 * The client passed O_NOATIME but we lack permissions to honor it. 168 * Rather than failing the open, fall back without O_NOATIME. This 169 * doesn't break the semantics on the client side, as the Linux 170 * open(2) man page notes that O_NOATIME "may not be effective on 171 * all filesystems". In particular, NFS and other network 172 * filesystems ignore it entirely. 173 */ 174 flags &= ~O_NOATIME; 175 goto again; 176 } 177 #endif 178 return -1; 179 } 180 181 /* Only if O_PATH is not set ... */ 182 if (!(flags & O_PATH_9P_UTIL)) { 183 /* 184 * Prevent I/O on special files (device files, etc.) on host side, 185 * however it is safe and required to allow opening them with O_PATH, 186 * as this is limited to (required) path based operations only. 187 */ 188 if (close_if_special_file(fd) < 0) { 189 return -1; 190 } 191 192 serrno = errno; 193 /* 194 * O_NONBLOCK was only needed to open the file. Let's drop it. We don't 195 * do that with O_PATH since fcntl(F_SETFL) isn't supported, and 196 * openat() ignored it anyway. 197 */ 198 ret = fcntl(fd, F_SETFL, flags); 199 assert(!ret); 200 errno = serrno; 201 } 202 return fd; 203 } 204 205 ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name, 206 void *value, size_t size); 207 int fsetxattrat_nofollow(int dirfd, const char *path, const char *name, 208 void *value, size_t size, int flags); 209 ssize_t flistxattrat_nofollow(int dirfd, const char *filename, 210 char *list, size_t size); 211 ssize_t fremovexattrat_nofollow(int dirfd, const char *filename, 212 const char *name); 213 214 /* 215 * Darwin has d_seekoff, which appears to function similarly to d_off. 216 * However, it does not appear to be supported on all file systems, 217 * so ensure it is manually injected earlier and call here when 218 * needed. 219 */ 220 static inline off_t qemu_dirent_off(struct dirent *dent) 221 { 222 #ifdef CONFIG_DARWIN 223 return dent->d_seekoff; 224 #else 225 return dent->d_off; 226 #endif 227 } 228 229 /** 230 * qemu_dirent_dup() - Duplicate directory entry @dent. 231 * 232 * @dent: original directory entry to be duplicated 233 * Return: duplicated directory entry which should be freed with g_free() 234 * 235 * It is highly recommended to use this function instead of open coding 236 * duplication of dirent objects, because the actual struct dirent 237 * size may be bigger or shorter than sizeof(struct dirent) and correct 238 * handling is platform specific (see gitlab issue #841). 239 */ 240 static inline struct dirent *qemu_dirent_dup(struct dirent *dent) 241 { 242 size_t sz = 0; 243 #if defined _DIRENT_HAVE_D_RECLEN 244 /* Avoid use of strlen() if platform supports d_reclen. */ 245 sz = dent->d_reclen; 246 #endif 247 /* 248 * Test sz for zero even if d_reclen is available 249 * because some drivers may set d_reclen to zero. 250 */ 251 if (sz == 0) { 252 /* Fallback to the most portable way. */ 253 sz = offsetof(struct dirent, d_name) + 254 strlen(dent->d_name) + 1; 255 } 256 return g_memdup(dent, sz); 257 } 258 259 /* 260 * As long as mknodat is not available on macOS, this workaround 261 * using pthread_fchdir_np is needed. qemu_mknodat is defined in 262 * os-posix.c. pthread_fchdir_np is weakly linked here as a guard 263 * in case it disappears in future macOS versions, because it is 264 * is a private API. 265 */ 266 #if defined CONFIG_DARWIN && defined CONFIG_PTHREAD_FCHDIR_NP 267 int pthread_fchdir_np(int fd) __attribute__((weak_import)); 268 #endif 269 int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev); 270 271 /* 272 * Returns a newly allocated string presentation of open() flags, intended 273 * for debugging (tracing) purposes only. 274 */ 275 char *qemu_open_flags_tostr(int flags); 276 277 #endif 278