1 /*- 2 * Copyright (c) 2009 Robert N. M. Watson 3 * All rights reserved. 4 * 5 * This software was developed at the University of Cambridge Computer 6 * Laboratory with support from a grant from Google, Inc. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 /*- 31 * FreeBSD process descriptor facility. 32 * 33 * Some processes are represented by a file descriptor, which will be used in 34 * preference to signaling and pids for the purposes of process management, 35 * and is, in effect, a form of capability. When a process descriptor is 36 * used with a process, it ceases to be visible to certain traditional UNIX 37 * process facilities, such as waitpid(2). 38 * 39 * Some semantics: 40 * 41 * - At most one process descriptor will exist for any process, although 42 * references to that descriptor may be held from many processes (or even 43 * be in flight between processes over a local domain socket). 44 * - Last close on the process descriptor will terminate the process using 45 * SIGKILL and reparent it to init so that there's a process to reap it 46 * when it's done exiting. 47 * - If the process exits before the descriptor is closed, it will not 48 * generate SIGCHLD on termination, or be picked up by waitpid(). 49 * - The pdkill(2) system call may be used to deliver a signal to the process 50 * using its process descriptor. 51 * - The pdwait4(2) system call may be used to block (or not) on a process 52 * descriptor to collect termination information. 53 * 54 * Open questions: 55 * 56 * - How to handle ptrace(2)? 57 * - Will we want to add a pidtoprocdesc(2) system call to allow process 58 * descriptors to be created for processes without pfork(2)? 59 */ 60 61 #include <sys/cdefs.h> 62 __FBSDID("$FreeBSD$"); 63 64 #include <sys/param.h> 65 #include <sys/capability.h> 66 #include <sys/fcntl.h> 67 #include <sys/file.h> 68 #include <sys/filedesc.h> 69 #include <sys/kernel.h> 70 #include <sys/lock.h> 71 #include <sys/mutex.h> 72 #include <sys/poll.h> 73 #include <sys/proc.h> 74 #include <sys/procdesc.h> 75 #include <sys/resourcevar.h> 76 #include <sys/stat.h> 77 #include <sys/sysproto.h> 78 #include <sys/sysctl.h> 79 #include <sys/systm.h> 80 #include <sys/ucred.h> 81 82 #include <security/audit/audit.h> 83 84 #include <vm/uma.h> 85 86 FEATURE(process_descriptors, "Process Descriptors"); 87 88 static uma_zone_t procdesc_zone; 89 90 static fo_rdwr_t procdesc_read; 91 static fo_rdwr_t procdesc_write; 92 static fo_truncate_t procdesc_truncate; 93 static fo_ioctl_t procdesc_ioctl; 94 static fo_poll_t procdesc_poll; 95 static fo_kqfilter_t procdesc_kqfilter; 96 static fo_stat_t procdesc_stat; 97 static fo_close_t procdesc_close; 98 static fo_chmod_t procdesc_chmod; 99 static fo_chown_t procdesc_chown; 100 101 static struct fileops procdesc_ops = { 102 .fo_read = procdesc_read, 103 .fo_write = procdesc_write, 104 .fo_truncate = procdesc_truncate, 105 .fo_ioctl = procdesc_ioctl, 106 .fo_poll = procdesc_poll, 107 .fo_kqfilter = procdesc_kqfilter, 108 .fo_stat = procdesc_stat, 109 .fo_close = procdesc_close, 110 .fo_chmod = procdesc_chmod, 111 .fo_chown = procdesc_chown, 112 .fo_sendfile = invfo_sendfile, 113 .fo_flags = DFLAG_PASSABLE, 114 }; 115 116 /* 117 * Initialize with VFS so that process descriptors are available along with 118 * other file descriptor types. As long as it runs before init(8) starts, 119 * there shouldn't be a problem. 120 */ 121 static void 122 procdesc_init(void *dummy __unused) 123 { 124 125 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc), 126 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 127 if (procdesc_zone == NULL) 128 panic("procdesc_init: procdesc_zone not initialized"); 129 } 130 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL); 131 132 /* 133 * Return a locked process given a process descriptor, or ESRCH if it has 134 * died. 135 */ 136 int 137 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 138 struct proc **p) 139 { 140 struct procdesc *pd; 141 struct file *fp; 142 int error; 143 144 error = fget(td, fd, rightsp, &fp); 145 if (error) 146 return (error); 147 if (fp->f_type != DTYPE_PROCDESC) { 148 error = EBADF; 149 goto out; 150 } 151 pd = fp->f_data; 152 sx_slock(&proctree_lock); 153 if (pd->pd_proc != NULL) { 154 *p = pd->pd_proc; 155 PROC_LOCK(*p); 156 } else 157 error = ESRCH; 158 sx_sunlock(&proctree_lock); 159 out: 160 fdrop(fp, td); 161 return (error); 162 } 163 164 /* 165 * Function to be used by procstat(1) sysctls when returning procdesc 166 * information. 167 */ 168 pid_t 169 procdesc_pid(struct file *fp_procdesc) 170 { 171 struct procdesc *pd; 172 173 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 174 ("procdesc_pid: !procdesc")); 175 176 pd = fp_procdesc->f_data; 177 return (pd->pd_pid); 178 } 179 180 /* 181 * Retrieve the PID associated with a process descriptor. 182 */ 183 int 184 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 185 { 186 struct file *fp; 187 int error; 188 189 error = fget(td, fd, rightsp, &fp); 190 if (error) 191 return (error); 192 if (fp->f_type != DTYPE_PROCDESC) { 193 error = EBADF; 194 goto out; 195 } 196 *pidp = procdesc_pid(fp); 197 out: 198 fdrop(fp, td); 199 return (error); 200 } 201 202 /* 203 * System call to return the pid of a process given its process descriptor. 204 */ 205 int 206 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 207 { 208 cap_rights_t rights; 209 pid_t pid; 210 int error; 211 212 AUDIT_ARG_FD(uap->fd); 213 error = kern_pdgetpid(td, uap->fd, 214 cap_rights_init(&rights, CAP_PDGETPID), &pid); 215 if (error == 0) 216 error = copyout(&pid, uap->pidp, sizeof(pid)); 217 return (error); 218 } 219 220 /* 221 * When a new process is forked by pdfork(), a file descriptor is allocated 222 * by the fork code first, then the process is forked, and then we get a 223 * chance to set up the process descriptor. Failure is not permitted at this 224 * point, so procdesc_new() must succeed. 225 */ 226 void 227 procdesc_new(struct proc *p, int flags) 228 { 229 struct procdesc *pd; 230 231 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO); 232 pd->pd_proc = p; 233 pd->pd_pid = p->p_pid; 234 p->p_procdesc = pd; 235 pd->pd_flags = 0; 236 if (flags & PD_DAEMON) 237 pd->pd_flags |= PDF_DAEMON; 238 PROCDESC_LOCK_INIT(pd); 239 240 /* 241 * Process descriptors start out with two references: one from their 242 * struct file, and the other from their struct proc. 243 */ 244 refcount_init(&pd->pd_refcount, 2); 245 } 246 247 /* 248 * Initialize a file with a process descriptor. 249 */ 250 void 251 procdesc_finit(struct procdesc *pdp, struct file *fp) 252 { 253 254 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 255 } 256 257 static void 258 procdesc_free(struct procdesc *pd) 259 { 260 261 /* 262 * When the last reference is released, we assert that the descriptor 263 * has been closed, but not that the process has exited, as we will 264 * detach the descriptor before the process dies if the descript is 265 * closed, as we can't wait synchronously. 266 */ 267 if (refcount_release(&pd->pd_refcount)) { 268 KASSERT(pd->pd_proc == NULL, 269 ("procdesc_free: pd_proc != NULL")); 270 KASSERT((pd->pd_flags & PDF_CLOSED), 271 ("procdesc_free: !PDF_CLOSED")); 272 273 PROCDESC_LOCK_DESTROY(pd); 274 uma_zfree(procdesc_zone, pd); 275 } 276 } 277 278 /* 279 * procdesc_exit() - notify a process descriptor that its process is exiting. 280 * We use the proctree_lock to ensure that process exit either happens 281 * strictly before or strictly after a concurrent call to procdesc_close(). 282 */ 283 int 284 procdesc_exit(struct proc *p) 285 { 286 struct procdesc *pd; 287 288 sx_assert(&proctree_lock, SA_XLOCKED); 289 PROC_LOCK_ASSERT(p, MA_OWNED); 290 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 291 292 pd = p->p_procdesc; 293 294 PROCDESC_LOCK(pd); 295 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc, 296 ("procdesc_exit: closed && parent not init")); 297 298 pd->pd_flags |= PDF_EXITED; 299 300 /* 301 * If the process descriptor has been closed, then we have nothing 302 * to do; return 1 so that init will get SIGCHLD and do the reaping. 303 * Clean up the procdesc now rather than letting it happen during 304 * that reap. 305 */ 306 if (pd->pd_flags & PDF_CLOSED) { 307 PROCDESC_UNLOCK(pd); 308 pd->pd_proc = NULL; 309 p->p_procdesc = NULL; 310 procdesc_free(pd); 311 return (1); 312 } 313 if (pd->pd_flags & PDF_SELECTED) { 314 pd->pd_flags &= ~PDF_SELECTED; 315 selwakeup(&pd->pd_selinfo); 316 } 317 PROCDESC_UNLOCK(pd); 318 return (0); 319 } 320 321 /* 322 * When a process descriptor is reaped, perhaps as a result of close() or 323 * pdwait4(), release the process's reference on the process descriptor. 324 */ 325 void 326 procdesc_reap(struct proc *p) 327 { 328 struct procdesc *pd; 329 330 sx_assert(&proctree_lock, SA_XLOCKED); 331 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 332 333 pd = p->p_procdesc; 334 pd->pd_proc = NULL; 335 p->p_procdesc = NULL; 336 procdesc_free(pd); 337 } 338 339 /* 340 * procdesc_close() - last close on a process descriptor. If the process is 341 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 342 * init(8) clean up the mess; if not, we have to clean up the zombie ourselves. 343 */ 344 static int 345 procdesc_close(struct file *fp, struct thread *td) 346 { 347 struct procdesc *pd; 348 struct proc *p; 349 350 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 351 352 pd = fp->f_data; 353 fp->f_ops = &badfileops; 354 fp->f_data = NULL; 355 356 sx_xlock(&proctree_lock); 357 PROCDESC_LOCK(pd); 358 pd->pd_flags |= PDF_CLOSED; 359 PROCDESC_UNLOCK(pd); 360 p = pd->pd_proc; 361 if (p == NULL) { 362 /* 363 * This is the case where process' exit status was already 364 * collected and procdesc_reap() was already called. 365 */ 366 sx_xunlock(&proctree_lock); 367 } else if (p->p_state == PRS_ZOMBIE) { 368 /* 369 * If the process is already dead and just awaiting reaping, 370 * do that now. This will release the process's reference to 371 * the process descriptor when it calls back into 372 * procdesc_reap(). 373 */ 374 PROC_LOCK(p); 375 PROC_SLOCK(p); 376 proc_reap(curthread, p, NULL, 0); 377 } else { 378 /* 379 * If the process is not yet dead, we need to kill it, but we 380 * can't wait around synchronously for it to go away, as that 381 * path leads to madness (and deadlocks). First, detach the 382 * process from its descriptor so that its exit status will 383 * be reported normally. 384 */ 385 PROC_LOCK(p); 386 pd->pd_proc = NULL; 387 p->p_procdesc = NULL; 388 procdesc_free(pd); 389 390 /* 391 * Next, reparent it to init(8) so that there's someone to 392 * pick up the pieces; finally, terminate with prejudice. 393 */ 394 p->p_sigparent = SIGCHLD; 395 proc_reparent(p, initproc); 396 if ((pd->pd_flags & PDF_DAEMON) == 0) 397 kern_psignal(p, SIGKILL); 398 PROC_UNLOCK(p); 399 sx_xunlock(&proctree_lock); 400 } 401 402 /* 403 * Release the file descriptor's reference on the process descriptor. 404 */ 405 procdesc_free(pd); 406 return (0); 407 } 408 409 static int 410 procdesc_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 411 int flags, struct thread *td) 412 { 413 414 return (EOPNOTSUPP); 415 } 416 417 static int 418 procdesc_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 419 int flags, struct thread *td) 420 { 421 422 return (EOPNOTSUPP); 423 } 424 425 static int 426 procdesc_truncate(struct file *fp, off_t length, struct ucred *active_cred, 427 struct thread *td) 428 { 429 430 return (EOPNOTSUPP); 431 } 432 433 static int 434 procdesc_ioctl(struct file *fp, u_long com, void *data, 435 struct ucred *active_cred, struct thread *td) 436 { 437 438 return (EOPNOTSUPP); 439 } 440 441 static int 442 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 443 struct thread *td) 444 { 445 struct procdesc *pd; 446 int revents; 447 448 revents = 0; 449 pd = fp->f_data; 450 PROCDESC_LOCK(pd); 451 if (pd->pd_flags & PDF_EXITED) 452 revents |= POLLHUP; 453 if (revents == 0) { 454 selrecord(td, &pd->pd_selinfo); 455 pd->pd_flags |= PDF_SELECTED; 456 } 457 PROCDESC_UNLOCK(pd); 458 return (revents); 459 } 460 461 static int 462 procdesc_kqfilter(struct file *fp, struct knote *kn) 463 { 464 465 return (EOPNOTSUPP); 466 } 467 468 static int 469 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 470 struct thread *td) 471 { 472 struct procdesc *pd; 473 struct timeval pstart; 474 475 /* 476 * XXXRW: Perhaps we should cache some more information from the 477 * process so that we can return it reliably here even after it has 478 * died. For example, caching its credential data. 479 */ 480 bzero(sb, sizeof(*sb)); 481 pd = fp->f_data; 482 sx_slock(&proctree_lock); 483 if (pd->pd_proc != NULL) { 484 PROC_LOCK(pd->pd_proc); 485 486 /* Set birth and [acm] times to process start time. */ 487 pstart = pd->pd_proc->p_stats->p_start; 488 timevaladd(&pstart, &boottime); 489 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 490 sb->st_atim = sb->st_birthtim; 491 sb->st_ctim = sb->st_birthtim; 492 sb->st_mtim = sb->st_birthtim; 493 if (pd->pd_proc->p_state != PRS_ZOMBIE) 494 sb->st_mode = S_IFREG | S_IRWXU; 495 else 496 sb->st_mode = S_IFREG; 497 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 498 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 499 PROC_UNLOCK(pd->pd_proc); 500 } else 501 sb->st_mode = S_IFREG; 502 sx_sunlock(&proctree_lock); 503 return (0); 504 } 505 506 static int 507 procdesc_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 508 struct thread *td) 509 { 510 511 return (EOPNOTSUPP); 512 } 513 514 static int 515 procdesc_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 516 struct thread *td) 517 { 518 519 return (EOPNOTSUPP); 520 } 521