1 /* 2 * Copyright (c) 2011 Comtrol Corp. 3 * Copyright (c) 2011-2018 The strace developers. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 */ 29 30 #include "defs.h" 31 #include <limits.h> 32 #include <poll.h> 33 34 #include "syscall.h" 35 #include "xstring.h" 36 37 struct path_set global_path_set; 38 39 /* 40 * Return true if specified path matches one that we're tracing. 41 */ 42 static bool 43 pathmatch(const char *path, struct path_set *set) 44 { 45 unsigned i; 46 47 for (i = 0; i < set->num_selected; ++i) { 48 if (strcmp(path, set->paths_selected[i]) == 0) 49 return true; 50 } 51 return false; 52 } 53 54 /* 55 * Return true if specified path (in user-space) matches. 56 */ 57 static bool 58 upathmatch(struct tcb *const tcp, const kernel_ulong_t upath, 59 struct path_set *set) 60 { 61 char path[PATH_MAX + 1]; 62 63 return umovestr(tcp, upath, sizeof(path), path) > 0 && 64 pathmatch(path, set); 65 } 66 67 /* 68 * Return true if specified fd maps to a path we're tracing. 69 */ 70 static bool 71 fdmatch(struct tcb *tcp, int fd, struct path_set *set) 72 { 73 char path[PATH_MAX + 1]; 74 int n = getfdpath(tcp, fd, path, sizeof(path)); 75 76 return n >= 0 && pathmatch(path, set); 77 } 78 79 /* 80 * Add a path to the set we're tracing. 81 * Specifying NULL will delete all paths. 82 */ 83 static void 84 storepath(const char *path, struct path_set *set) 85 { 86 if (pathmatch(path, set)) 87 return; /* already in table */ 88 89 if (set->num_selected >= set->size) 90 set->paths_selected = 91 xgrowarray(set->paths_selected, &set->size, 92 sizeof(set->paths_selected[0])); 93 94 set->paths_selected[set->num_selected++] = path; 95 } 96 97 /* 98 * Get path associated with fd. 99 */ 100 int 101 getfdpath(struct tcb *tcp, int fd, char *buf, unsigned bufsize) 102 { 103 char linkpath[sizeof("/proc/%u/fd/%u") + 2 * sizeof(int)*3]; 104 ssize_t n; 105 106 if (fd < 0) 107 return -1; 108 109 xsprintf(linkpath, "/proc/%u/fd/%u", tcp->pid, fd); 110 n = readlink(linkpath, buf, bufsize - 1); 111 /* 112 * NB: if buf is too small, readlink doesn't fail, 113 * it returns truncated result (IOW: n == bufsize - 1). 114 */ 115 if (n >= 0) 116 buf[n] = '\0'; 117 return n; 118 } 119 120 /* 121 * Add a path to the set we're tracing. Also add the canonicalized 122 * version of the path. Specifying NULL will delete all paths. 123 */ 124 void 125 pathtrace_select_set(const char *path, struct path_set *set) 126 { 127 char *rpath; 128 129 storepath(path, set); 130 131 rpath = realpath(path, NULL); 132 133 if (rpath == NULL) 134 return; 135 136 /* if realpath and specified path are same, we're done */ 137 if (strcmp(path, rpath) == 0) { 138 free(rpath); 139 return; 140 } 141 142 error_msg("Requested path '%s' resolved into '%s'", path, rpath); 143 storepath(rpath, set); 144 } 145 146 static bool 147 match_xselect_args(struct tcb *tcp, const kernel_ulong_t *args, 148 struct path_set *set) 149 { 150 /* Kernel truncates arg[0] to int, we do the same. */ 151 int nfds = (int) args[0]; 152 /* Kernel rejects negative nfds, so we don't parse it either. */ 153 if (nfds <= 0) 154 return false; 155 /* Beware of select(2^31-1, NULL, NULL, NULL) and similar... */ 156 if (nfds > 1024*1024) 157 nfds = 1024*1024; 158 unsigned int fdsize = (((nfds + 7) / 8) + current_wordsize-1) & -current_wordsize; 159 fd_set *fds = xmalloc(fdsize); 160 161 for (unsigned int i = 1; i <= 3; ++i) { 162 if (args[i] == 0) 163 continue; 164 if (umoven(tcp, args[i], fdsize, fds) < 0) 165 continue; 166 for (int j = 0;; ++j) { 167 j = next_set_bit(fds, j, nfds); 168 if (j < 0) 169 break; 170 if (fdmatch(tcp, j, set)) { 171 free(fds); 172 return true; 173 } 174 } 175 } 176 177 free(fds); 178 return false; 179 } 180 181 /* 182 * Return true if syscall accesses a selected path 183 * (or if no paths have been specified for tracing). 184 */ 185 bool 186 pathtrace_match_set(struct tcb *tcp, struct path_set *set) 187 { 188 const struct_sysent *s; 189 190 s = tcp->s_ent; 191 192 if (!(s->sys_flags & (TRACE_FILE | TRACE_DESC | TRACE_NETWORK))) 193 return false; 194 195 /* 196 * Check for special cases where we need to do something 197 * other than test arg[0]. 198 */ 199 200 switch (s->sen) { 201 case SEN_dup2: 202 case SEN_dup3: 203 case SEN_kexec_file_load: 204 case SEN_sendfile: 205 case SEN_sendfile64: 206 case SEN_tee: 207 /* fd, fd */ 208 return fdmatch(tcp, tcp->u_arg[0], set) || 209 fdmatch(tcp, tcp->u_arg[1], set); 210 211 case SEN_execveat: 212 case SEN_faccessat: 213 case SEN_fchmodat: 214 case SEN_fchownat: 215 case SEN_fstatat64: 216 case SEN_futimesat: 217 case SEN_inotify_add_watch: 218 case SEN_mkdirat: 219 case SEN_mknodat: 220 case SEN_name_to_handle_at: 221 case SEN_newfstatat: 222 case SEN_openat: 223 case SEN_readlinkat: 224 case SEN_statx: 225 case SEN_unlinkat: 226 case SEN_utimensat: 227 /* fd, path */ 228 return fdmatch(tcp, tcp->u_arg[0], set) || 229 upathmatch(tcp, tcp->u_arg[1], set); 230 231 case SEN_link: 232 case SEN_mount: 233 case SEN_pivotroot: 234 /* path, path */ 235 return upathmatch(tcp, tcp->u_arg[0], set) || 236 upathmatch(tcp, tcp->u_arg[1], set); 237 238 case SEN_quotactl: 239 case SEN_symlink: 240 /* x, path */ 241 return upathmatch(tcp, tcp->u_arg[1], set); 242 243 case SEN_linkat: 244 case SEN_renameat2: 245 case SEN_renameat: 246 /* fd, path, fd, path */ 247 return fdmatch(tcp, tcp->u_arg[0], set) || 248 fdmatch(tcp, tcp->u_arg[2], set) || 249 upathmatch(tcp, tcp->u_arg[1], set) || 250 upathmatch(tcp, tcp->u_arg[3], set); 251 252 #if HAVE_ARCH_OLD_MMAP 253 case SEN_old_mmap: 254 # if HAVE_ARCH_OLD_MMAP_PGOFF 255 case SEN_old_mmap_pgoff: 256 # endif 257 { 258 kernel_ulong_t *args = 259 fetch_indirect_syscall_args(tcp, tcp->u_arg[0], 6); 260 261 return args && fdmatch(tcp, args[4], set); 262 } 263 #endif /* HAVE_ARCH_OLD_MMAP */ 264 265 case SEN_mmap: 266 case SEN_mmap_4koff: 267 case SEN_mmap_pgoff: 268 case SEN_ARCH_mmap: 269 /* x, x, x, x, fd */ 270 return fdmatch(tcp, tcp->u_arg[4], set); 271 272 case SEN_symlinkat: 273 /* x, fd, path */ 274 return fdmatch(tcp, tcp->u_arg[1], set) || 275 upathmatch(tcp, tcp->u_arg[2], set); 276 277 case SEN_copy_file_range: 278 case SEN_splice: 279 /* fd, x, fd, x, x, x */ 280 return fdmatch(tcp, tcp->u_arg[0], set) || 281 fdmatch(tcp, tcp->u_arg[2], set); 282 283 case SEN_epoll_ctl: 284 /* x, x, fd, x */ 285 return fdmatch(tcp, tcp->u_arg[2], set); 286 287 288 case SEN_fanotify_mark: 289 { 290 /* x, x, mask (64 bit), fd, path */ 291 unsigned long long mask = 0; 292 int argn = getllval(tcp, &mask, 2); 293 return fdmatch(tcp, tcp->u_arg[argn], set) || 294 upathmatch(tcp, tcp->u_arg[argn + 1], set); 295 } 296 #if HAVE_ARCH_OLD_SELECT 297 case SEN_oldselect: 298 { 299 kernel_ulong_t *args = 300 fetch_indirect_syscall_args(tcp, tcp->u_arg[0], 5); 301 302 return args && match_xselect_args(tcp, args, set); 303 } 304 #endif 305 case SEN_pselect6: 306 case SEN_select: 307 return match_xselect_args(tcp, tcp->u_arg, set); 308 case SEN_poll: 309 case SEN_ppoll: 310 { 311 struct pollfd fds; 312 unsigned nfds; 313 kernel_ulong_t start, cur, end; 314 315 start = tcp->u_arg[0]; 316 nfds = tcp->u_arg[1]; 317 318 if (nfds > 1024 * 1024) 319 nfds = 1024 * 1024; 320 end = start + sizeof(fds) * nfds; 321 322 if (nfds == 0 || end < start) 323 return false; 324 325 for (cur = start; cur < end; cur += sizeof(fds)) { 326 if (umove(tcp, cur, &fds)) 327 break; 328 if (fdmatch(tcp, fds.fd, set)) 329 return true; 330 } 331 332 return false; 333 } 334 335 case SEN_accept4: 336 case SEN_accept: 337 case SEN_bpf: 338 case SEN_epoll_create: 339 case SEN_epoll_create1: 340 case SEN_eventfd2: 341 case SEN_eventfd: 342 case SEN_fanotify_init: 343 case SEN_inotify_init: 344 case SEN_inotify_init1: 345 case SEN_memfd_create: 346 case SEN_mq_getsetattr: 347 case SEN_mq_notify: 348 case SEN_mq_open: 349 case SEN_mq_timedreceive: 350 case SEN_mq_timedsend: 351 case SEN_perf_event_open: 352 case SEN_pipe: 353 case SEN_pipe2: 354 case SEN_printargs: 355 case SEN_signalfd4: 356 case SEN_signalfd: 357 case SEN_socket: 358 case SEN_socketpair: 359 case SEN_timerfd_create: 360 case SEN_timerfd_gettime: 361 case SEN_timerfd_settime: 362 case SEN_userfaultfd: 363 /* 364 * These have TRACE_FILE or TRACE_DESCRIPTOR or TRACE_NETWORK set, 365 * but they don't have any file descriptor or path args to test. 366 */ 367 return false; 368 } 369 370 /* 371 * Our fallback position for calls that haven't already 372 * been handled is to just check arg[0]. 373 */ 374 375 if (s->sys_flags & TRACE_FILE) 376 return upathmatch(tcp, tcp->u_arg[0], set); 377 378 if (s->sys_flags & (TRACE_DESC | TRACE_NETWORK)) 379 return fdmatch(tcp, tcp->u_arg[0], set); 380 381 return false; 382 } 383
