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 "opt_procdesc.h" 65 66 #include <sys/param.h> 67 #include <sys/capability.h> 68 #include <sys/fcntl.h> 69 #include <sys/file.h> 70 #include <sys/filedesc.h> 71 #include <sys/kernel.h> 72 #include <sys/lock.h> 73 #include <sys/mutex.h> 74 #include <sys/poll.h> 75 #include <sys/proc.h> 76 #include <sys/procdesc.h> 77 #include <sys/resourcevar.h> 78 #include <sys/stat.h> 79 #include <sys/sysproto.h> 80 #include <sys/sysctl.h> 81 #include <sys/systm.h> 82 #include <sys/ucred.h> 83 84 #include <security/audit/audit.h> 85 86 #include <vm/uma.h> 87 88 #ifdef PROCDESC 89 90 FEATURE(process_descriptors, "Process Descriptors"); 91 92 static uma_zone_t procdesc_zone; 93 94 static fo_rdwr_t procdesc_read; 95 static fo_rdwr_t procdesc_write; 96 static fo_truncate_t procdesc_truncate; 97 static fo_ioctl_t procdesc_ioctl; 98 static fo_poll_t procdesc_poll; 99 static fo_kqfilter_t procdesc_kqfilter; 100 static fo_stat_t procdesc_stat; 101 static fo_close_t procdesc_close; 102 static fo_chmod_t procdesc_chmod; 103 static fo_chown_t procdesc_chown; 104 105 static struct fileops procdesc_ops = { 106 .fo_read = procdesc_read, 107 .fo_write = procdesc_write, 108 .fo_truncate = procdesc_truncate, 109 .fo_ioctl = procdesc_ioctl, 110 .fo_poll = procdesc_poll, 111 .fo_kqfilter = procdesc_kqfilter, 112 .fo_stat = procdesc_stat, 113 .fo_close = procdesc_close, 114 .fo_chmod = procdesc_chmod, 115 .fo_chown = procdesc_chown, 116 .fo_flags = DFLAG_PASSABLE, 117 }; 118 119 /* 120 * Initialize with VFS so that process descriptors are available along with 121 * other file descriptor types. As long as it runs before init(8) starts, 122 * there shouldn't be a problem. 123 */ 124 static void 125 procdesc_init(void *dummy __unused) 126 { 127 128 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc), 129 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 130 if (procdesc_zone == NULL) 131 panic("procdesc_init: procdesc_zone not initialized"); 132 } 133 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL); 134 135 /* 136 * Return a locked process given a process descriptor, or ESRCH if it has 137 * died. 138 */ 139 int 140 procdesc_find(struct thread *td, int fd, cap_rights_t rights, 141 struct proc **p) 142 { 143 struct procdesc *pd; 144 struct file *fp; 145 int error; 146 147 error = fget(td, fd, rights, &fp); 148 if (error) 149 return (error); 150 if (fp->f_type != DTYPE_PROCDESC) { 151 error = EBADF; 152 goto out; 153 } 154 pd = fp->f_data; 155 sx_slock(&proctree_lock); 156 if (pd->pd_proc != NULL) { 157 *p = pd->pd_proc; 158 PROC_LOCK(*p); 159 } else 160 error = ESRCH; 161 sx_sunlock(&proctree_lock); 162 out: 163 fdrop(fp, td); 164 return (error); 165 } 166 167 /* 168 * Function to be used by procstat(1) sysctls when returning procdesc 169 * information. 170 */ 171 pid_t 172 procdesc_pid(struct file *fp_procdesc) 173 { 174 struct procdesc *pd; 175 176 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 177 ("procdesc_pid: !procdesc")); 178 179 pd = fp_procdesc->f_data; 180 return (pd->pd_pid); 181 } 182 183 /* 184 * Retrieve the PID associated with a process descriptor. 185 */ 186 int 187 kern_pdgetpid(struct thread *td, int fd, cap_rights_t rights, pid_t *pidp) 188 { 189 struct file *fp; 190 int error; 191 192 error = fget(td, fd, rights, &fp); 193 if (error) 194 return (error); 195 if (fp->f_type != DTYPE_PROCDESC) { 196 error = EBADF; 197 goto out; 198 } 199 *pidp = procdesc_pid(fp); 200 out: 201 fdrop(fp, td); 202 return (error); 203 } 204 205 /* 206 * System call to return the pid of a process given its process descriptor. 207 */ 208 int 209 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 210 { 211 pid_t pid; 212 int error; 213 214 AUDIT_ARG_FD(uap->fd); 215 error = kern_pdgetpid(td, uap->fd, CAP_PDGETPID, &pid); 216 if (error == 0) 217 error = copyout(&pid, uap->pidp, sizeof(pid)); 218 return (error); 219 } 220 221 /* 222 * When a new process is forked by pdfork(), a file descriptor is allocated 223 * by the fork code first, then the process is forked, and then we get a 224 * chance to set up the process descriptor. Failure is not permitted at this 225 * point, so procdesc_new() must succeed. 226 */ 227 void 228 procdesc_new(struct proc *p, int flags) 229 { 230 struct procdesc *pd; 231 232 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO); 233 pd->pd_proc = p; 234 pd->pd_pid = p->p_pid; 235 p->p_procdesc = pd; 236 pd->pd_flags = 0; 237 if (flags & PD_DAEMON) 238 pd->pd_flags |= PDF_DAEMON; 239 PROCDESC_LOCK_INIT(pd); 240 241 /* 242 * Process descriptors start out with two references: one from their 243 * struct file, and the other from their struct proc. 244 */ 245 refcount_init(&pd->pd_refcount, 2); 246 } 247 248 /* 249 * Initialize a file with a process descriptor. 250 */ 251 void 252 procdesc_finit(struct procdesc *pdp, struct file *fp) 253 { 254 255 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 256 } 257 258 static void 259 procdesc_free(struct procdesc *pd) 260 { 261 262 /* 263 * When the last reference is released, we assert that the descriptor 264 * has been closed, but not that the process has exited, as we will 265 * detach the descriptor before the process dies if the descript is 266 * closed, as we can't wait synchronously. 267 */ 268 if (refcount_release(&pd->pd_refcount)) { 269 KASSERT(pd->pd_proc == NULL, 270 ("procdesc_free: pd_proc != NULL")); 271 KASSERT((pd->pd_flags & PDF_CLOSED), 272 ("procdesc_free: !PDF_CLOSED")); 273 274 PROCDESC_LOCK_DESTROY(pd); 275 uma_zfree(procdesc_zone, pd); 276 } 277 } 278 279 /* 280 * procdesc_exit() - notify a process descriptor that its process is exiting. 281 * We use the proctree_lock to ensure that process exit either happens 282 * strictly before or strictly after a concurrent call to procdesc_close(). 283 */ 284 int 285 procdesc_exit(struct proc *p) 286 { 287 struct procdesc *pd; 288 289 sx_assert(&proctree_lock, SA_XLOCKED); 290 PROC_LOCK_ASSERT(p, MA_OWNED); 291 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 292 293 pd = p->p_procdesc; 294 295 PROCDESC_LOCK(pd); 296 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc, 297 ("procdesc_exit: closed && parent not init")); 298 299 pd->pd_flags |= PDF_EXITED; 300 301 /* 302 * If the process descriptor has been closed, then we have nothing 303 * to do; return 1 so that init will get SIGCHLD and do the reaping. 304 * Clean up the procdesc now rather than letting it happen during 305 * that reap. 306 */ 307 if (pd->pd_flags & PDF_CLOSED) { 308 PROCDESC_UNLOCK(pd); 309 pd->pd_proc = NULL; 310 p->p_procdesc = NULL; 311 procdesc_free(pd); 312 return (1); 313 } 314 if (pd->pd_flags & PDF_SELECTED) { 315 pd->pd_flags &= ~PDF_SELECTED; 316 selwakeup(&pd->pd_selinfo); 317 } 318 PROCDESC_UNLOCK(pd); 319 return (0); 320 } 321 322 /* 323 * When a process descriptor is reaped, perhaps as a result of close() or 324 * pdwait4(), release the process's reference on the process descriptor. 325 */ 326 void 327 procdesc_reap(struct proc *p) 328 { 329 struct procdesc *pd; 330 331 sx_assert(&proctree_lock, SA_XLOCKED); 332 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 333 334 pd = p->p_procdesc; 335 pd->pd_proc = NULL; 336 p->p_procdesc = NULL; 337 procdesc_free(pd); 338 } 339 340 /* 341 * procdesc_close() - last close on a process descriptor. If the process is 342 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 343 * init(8) clean up the mess; if not, we have to clean up the zombie ourselves. 344 */ 345 static int 346 procdesc_close(struct file *fp, struct thread *td) 347 { 348 struct procdesc *pd; 349 struct proc *p; 350 351 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 352 353 pd = fp->f_data; 354 fp->f_ops = &badfileops; 355 fp->f_data = NULL; 356 357 sx_xlock(&proctree_lock); 358 PROCDESC_LOCK(pd); 359 pd->pd_flags |= PDF_CLOSED; 360 PROCDESC_UNLOCK(pd); 361 p = pd->pd_proc; 362 if (p == NULL) { 363 /* 364 * This is the case where process' exit status was already 365 * collected and procdesc_reap() was already called. 366 */ 367 sx_xunlock(&proctree_lock); 368 } else if (p->p_state == PRS_ZOMBIE) { 369 /* 370 * If the process is already dead and just awaiting reaping, 371 * do that now. This will release the process's reference to 372 * the process descriptor when it calls back into 373 * procdesc_reap(). 374 */ 375 PROC_LOCK(p); 376 PROC_SLOCK(p); 377 proc_reap(curthread, p, NULL, 0); 378 } else { 379 /* 380 * If the process is not yet dead, we need to kill it, but we 381 * can't wait around synchronously for it to go away, as that 382 * path leads to madness (and deadlocks). First, detach the 383 * process from its descriptor so that its exit status will 384 * be reported normally. 385 */ 386 PROC_LOCK(p); 387 pd->pd_proc = NULL; 388 p->p_procdesc = NULL; 389 procdesc_free(pd); 390 391 /* 392 * Next, reparent it to init(8) so that there's someone to 393 * pick up the pieces; finally, terminate with prejudice. 394 */ 395 p->p_sigparent = SIGCHLD; 396 proc_reparent(p, initproc); 397 if ((pd->pd_flags & PDF_DAEMON) == 0) 398 kern_psignal(p, SIGKILL); 399 PROC_UNLOCK(p); 400 sx_xunlock(&proctree_lock); 401 } 402 403 /* 404 * Release the file descriptor's reference on the process descriptor. 405 */ 406 procdesc_free(pd); 407 return (0); 408 } 409 410 static int 411 procdesc_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 412 int flags, struct thread *td) 413 { 414 415 return (EOPNOTSUPP); 416 } 417 418 static int 419 procdesc_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 420 int flags, struct thread *td) 421 { 422 423 return (EOPNOTSUPP); 424 } 425 426 static int 427 procdesc_truncate(struct file *fp, off_t length, struct ucred *active_cred, 428 struct thread *td) 429 { 430 431 return (EOPNOTSUPP); 432 } 433 434 static int 435 procdesc_ioctl(struct file *fp, u_long com, void *data, 436 struct ucred *active_cred, struct thread *td) 437 { 438 439 return (EOPNOTSUPP); 440 } 441 442 static int 443 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 444 struct thread *td) 445 { 446 struct procdesc *pd; 447 int revents; 448 449 revents = 0; 450 pd = fp->f_data; 451 PROCDESC_LOCK(pd); 452 if (pd->pd_flags & PDF_EXITED) 453 revents |= POLLHUP; 454 if (revents == 0) { 455 selrecord(td, &pd->pd_selinfo); 456 pd->pd_flags |= PDF_SELECTED; 457 } 458 PROCDESC_UNLOCK(pd); 459 return (revents); 460 } 461 462 static int 463 procdesc_kqfilter(struct file *fp, struct knote *kn) 464 { 465 466 return (EOPNOTSUPP); 467 } 468 469 static int 470 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 471 struct thread *td) 472 { 473 struct procdesc *pd; 474 struct timeval pstart; 475 476 /* 477 * XXXRW: Perhaps we should cache some more information from the 478 * process so that we can return it reliably here even after it has 479 * died. For example, caching its credential data. 480 */ 481 bzero(sb, sizeof(*sb)); 482 pd = fp->f_data; 483 sx_slock(&proctree_lock); 484 if (pd->pd_proc != NULL) { 485 PROC_LOCK(pd->pd_proc); 486 487 /* Set birth and [acm] times to process start time. */ 488 pstart = pd->pd_proc->p_stats->p_start; 489 timevaladd(&pstart, &boottime); 490 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 491 sb->st_atim = sb->st_birthtim; 492 sb->st_ctim = sb->st_birthtim; 493 sb->st_mtim = sb->st_birthtim; 494 if (pd->pd_proc->p_state != PRS_ZOMBIE) 495 sb->st_mode = S_IFREG | S_IRWXU; 496 else 497 sb->st_mode = S_IFREG; 498 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 499 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 500 PROC_UNLOCK(pd->pd_proc); 501 } else 502 sb->st_mode = S_IFREG; 503 sx_sunlock(&proctree_lock); 504 return (0); 505 } 506 507 static int 508 procdesc_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 509 struct thread *td) 510 { 511 512 return (EOPNOTSUPP); 513 } 514 515 static int 516 procdesc_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 517 struct thread *td) 518 { 519 520 return (EOPNOTSUPP); 521 } 522 523 #else /* !PROCDESC */ 524 525 int 526 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 527 { 528 529 return (ENOSYS); 530 } 531 532 #endif /* PROCDESC */ 533