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_sendfile = invfo_sendfile, 117 .fo_flags = DFLAG_PASSABLE, 118 }; 119 120 /* 121 * Initialize with VFS so that process descriptors are available along with 122 * other file descriptor types. As long as it runs before init(8) starts, 123 * there shouldn't be a problem. 124 */ 125 static void 126 procdesc_init(void *dummy __unused) 127 { 128 129 procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc), 130 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 131 if (procdesc_zone == NULL) 132 panic("procdesc_init: procdesc_zone not initialized"); 133 } 134 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL); 135 136 /* 137 * Return a locked process given a process descriptor, or ESRCH if it has 138 * died. 139 */ 140 int 141 procdesc_find(struct thread *td, int fd, cap_rights_t *rightsp, 142 struct proc **p) 143 { 144 struct procdesc *pd; 145 struct file *fp; 146 int error; 147 148 error = fget(td, fd, rightsp, &fp); 149 if (error) 150 return (error); 151 if (fp->f_type != DTYPE_PROCDESC) { 152 error = EBADF; 153 goto out; 154 } 155 pd = fp->f_data; 156 sx_slock(&proctree_lock); 157 if (pd->pd_proc != NULL) { 158 *p = pd->pd_proc; 159 PROC_LOCK(*p); 160 } else 161 error = ESRCH; 162 sx_sunlock(&proctree_lock); 163 out: 164 fdrop(fp, td); 165 return (error); 166 } 167 168 /* 169 * Function to be used by procstat(1) sysctls when returning procdesc 170 * information. 171 */ 172 pid_t 173 procdesc_pid(struct file *fp_procdesc) 174 { 175 struct procdesc *pd; 176 177 KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC, 178 ("procdesc_pid: !procdesc")); 179 180 pd = fp_procdesc->f_data; 181 return (pd->pd_pid); 182 } 183 184 /* 185 * Retrieve the PID associated with a process descriptor. 186 */ 187 int 188 kern_pdgetpid(struct thread *td, int fd, cap_rights_t *rightsp, pid_t *pidp) 189 { 190 struct file *fp; 191 int error; 192 193 error = fget(td, fd, rightsp, &fp); 194 if (error) 195 return (error); 196 if (fp->f_type != DTYPE_PROCDESC) { 197 error = EBADF; 198 goto out; 199 } 200 *pidp = procdesc_pid(fp); 201 out: 202 fdrop(fp, td); 203 return (error); 204 } 205 206 /* 207 * System call to return the pid of a process given its process descriptor. 208 */ 209 int 210 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 211 { 212 cap_rights_t rights; 213 pid_t pid; 214 int error; 215 216 AUDIT_ARG_FD(uap->fd); 217 error = kern_pdgetpid(td, uap->fd, 218 cap_rights_init(&rights, CAP_PDGETPID), &pid); 219 if (error == 0) 220 error = copyout(&pid, uap->pidp, sizeof(pid)); 221 return (error); 222 } 223 224 /* 225 * When a new process is forked by pdfork(), a file descriptor is allocated 226 * by the fork code first, then the process is forked, and then we get a 227 * chance to set up the process descriptor. Failure is not permitted at this 228 * point, so procdesc_new() must succeed. 229 */ 230 void 231 procdesc_new(struct proc *p, int flags) 232 { 233 struct procdesc *pd; 234 235 pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO); 236 pd->pd_proc = p; 237 pd->pd_pid = p->p_pid; 238 p->p_procdesc = pd; 239 pd->pd_flags = 0; 240 if (flags & PD_DAEMON) 241 pd->pd_flags |= PDF_DAEMON; 242 PROCDESC_LOCK_INIT(pd); 243 244 /* 245 * Process descriptors start out with two references: one from their 246 * struct file, and the other from their struct proc. 247 */ 248 refcount_init(&pd->pd_refcount, 2); 249 } 250 251 /* 252 * Initialize a file with a process descriptor. 253 */ 254 void 255 procdesc_finit(struct procdesc *pdp, struct file *fp) 256 { 257 258 finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops); 259 } 260 261 static void 262 procdesc_free(struct procdesc *pd) 263 { 264 265 /* 266 * When the last reference is released, we assert that the descriptor 267 * has been closed, but not that the process has exited, as we will 268 * detach the descriptor before the process dies if the descript is 269 * closed, as we can't wait synchronously. 270 */ 271 if (refcount_release(&pd->pd_refcount)) { 272 KASSERT(pd->pd_proc == NULL, 273 ("procdesc_free: pd_proc != NULL")); 274 KASSERT((pd->pd_flags & PDF_CLOSED), 275 ("procdesc_free: !PDF_CLOSED")); 276 277 PROCDESC_LOCK_DESTROY(pd); 278 uma_zfree(procdesc_zone, pd); 279 } 280 } 281 282 /* 283 * procdesc_exit() - notify a process descriptor that its process is exiting. 284 * We use the proctree_lock to ensure that process exit either happens 285 * strictly before or strictly after a concurrent call to procdesc_close(). 286 */ 287 int 288 procdesc_exit(struct proc *p) 289 { 290 struct procdesc *pd; 291 292 sx_assert(&proctree_lock, SA_XLOCKED); 293 PROC_LOCK_ASSERT(p, MA_OWNED); 294 KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL")); 295 296 pd = p->p_procdesc; 297 298 PROCDESC_LOCK(pd); 299 KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc, 300 ("procdesc_exit: closed && parent not init")); 301 302 pd->pd_flags |= PDF_EXITED; 303 304 /* 305 * If the process descriptor has been closed, then we have nothing 306 * to do; return 1 so that init will get SIGCHLD and do the reaping. 307 * Clean up the procdesc now rather than letting it happen during 308 * that reap. 309 */ 310 if (pd->pd_flags & PDF_CLOSED) { 311 PROCDESC_UNLOCK(pd); 312 pd->pd_proc = NULL; 313 p->p_procdesc = NULL; 314 procdesc_free(pd); 315 return (1); 316 } 317 if (pd->pd_flags & PDF_SELECTED) { 318 pd->pd_flags &= ~PDF_SELECTED; 319 selwakeup(&pd->pd_selinfo); 320 } 321 PROCDESC_UNLOCK(pd); 322 return (0); 323 } 324 325 /* 326 * When a process descriptor is reaped, perhaps as a result of close() or 327 * pdwait4(), release the process's reference on the process descriptor. 328 */ 329 void 330 procdesc_reap(struct proc *p) 331 { 332 struct procdesc *pd; 333 334 sx_assert(&proctree_lock, SA_XLOCKED); 335 KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL")); 336 337 pd = p->p_procdesc; 338 pd->pd_proc = NULL; 339 p->p_procdesc = NULL; 340 procdesc_free(pd); 341 } 342 343 /* 344 * procdesc_close() - last close on a process descriptor. If the process is 345 * still running, terminate with SIGKILL (unless PDF_DAEMON is set) and let 346 * init(8) clean up the mess; if not, we have to clean up the zombie ourselves. 347 */ 348 static int 349 procdesc_close(struct file *fp, struct thread *td) 350 { 351 struct procdesc *pd; 352 struct proc *p; 353 354 KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc")); 355 356 pd = fp->f_data; 357 fp->f_ops = &badfileops; 358 fp->f_data = NULL; 359 360 sx_xlock(&proctree_lock); 361 PROCDESC_LOCK(pd); 362 pd->pd_flags |= PDF_CLOSED; 363 PROCDESC_UNLOCK(pd); 364 p = pd->pd_proc; 365 if (p == NULL) { 366 /* 367 * This is the case where process' exit status was already 368 * collected and procdesc_reap() was already called. 369 */ 370 sx_xunlock(&proctree_lock); 371 } else if (p->p_state == PRS_ZOMBIE) { 372 /* 373 * If the process is already dead and just awaiting reaping, 374 * do that now. This will release the process's reference to 375 * the process descriptor when it calls back into 376 * procdesc_reap(). 377 */ 378 PROC_LOCK(p); 379 PROC_SLOCK(p); 380 proc_reap(curthread, p, NULL, 0); 381 } else { 382 /* 383 * If the process is not yet dead, we need to kill it, but we 384 * can't wait around synchronously for it to go away, as that 385 * path leads to madness (and deadlocks). First, detach the 386 * process from its descriptor so that its exit status will 387 * be reported normally. 388 */ 389 PROC_LOCK(p); 390 pd->pd_proc = NULL; 391 p->p_procdesc = NULL; 392 procdesc_free(pd); 393 394 /* 395 * Next, reparent it to init(8) so that there's someone to 396 * pick up the pieces; finally, terminate with prejudice. 397 */ 398 p->p_sigparent = SIGCHLD; 399 proc_reparent(p, initproc); 400 if ((pd->pd_flags & PDF_DAEMON) == 0) 401 kern_psignal(p, SIGKILL); 402 PROC_UNLOCK(p); 403 sx_xunlock(&proctree_lock); 404 } 405 406 /* 407 * Release the file descriptor's reference on the process descriptor. 408 */ 409 procdesc_free(pd); 410 return (0); 411 } 412 413 static int 414 procdesc_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 415 int flags, struct thread *td) 416 { 417 418 return (EOPNOTSUPP); 419 } 420 421 static int 422 procdesc_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 423 int flags, struct thread *td) 424 { 425 426 return (EOPNOTSUPP); 427 } 428 429 static int 430 procdesc_truncate(struct file *fp, off_t length, struct ucred *active_cred, 431 struct thread *td) 432 { 433 434 return (EOPNOTSUPP); 435 } 436 437 static int 438 procdesc_ioctl(struct file *fp, u_long com, void *data, 439 struct ucred *active_cred, struct thread *td) 440 { 441 442 return (EOPNOTSUPP); 443 } 444 445 static int 446 procdesc_poll(struct file *fp, int events, struct ucred *active_cred, 447 struct thread *td) 448 { 449 struct procdesc *pd; 450 int revents; 451 452 revents = 0; 453 pd = fp->f_data; 454 PROCDESC_LOCK(pd); 455 if (pd->pd_flags & PDF_EXITED) 456 revents |= POLLHUP; 457 if (revents == 0) { 458 selrecord(td, &pd->pd_selinfo); 459 pd->pd_flags |= PDF_SELECTED; 460 } 461 PROCDESC_UNLOCK(pd); 462 return (revents); 463 } 464 465 static int 466 procdesc_kqfilter(struct file *fp, struct knote *kn) 467 { 468 469 return (EOPNOTSUPP); 470 } 471 472 static int 473 procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 474 struct thread *td) 475 { 476 struct procdesc *pd; 477 struct timeval pstart; 478 479 /* 480 * XXXRW: Perhaps we should cache some more information from the 481 * process so that we can return it reliably here even after it has 482 * died. For example, caching its credential data. 483 */ 484 bzero(sb, sizeof(*sb)); 485 pd = fp->f_data; 486 sx_slock(&proctree_lock); 487 if (pd->pd_proc != NULL) { 488 PROC_LOCK(pd->pd_proc); 489 490 /* Set birth and [acm] times to process start time. */ 491 pstart = pd->pd_proc->p_stats->p_start; 492 timevaladd(&pstart, &boottime); 493 TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim); 494 sb->st_atim = sb->st_birthtim; 495 sb->st_ctim = sb->st_birthtim; 496 sb->st_mtim = sb->st_birthtim; 497 if (pd->pd_proc->p_state != PRS_ZOMBIE) 498 sb->st_mode = S_IFREG | S_IRWXU; 499 else 500 sb->st_mode = S_IFREG; 501 sb->st_uid = pd->pd_proc->p_ucred->cr_ruid; 502 sb->st_gid = pd->pd_proc->p_ucred->cr_rgid; 503 PROC_UNLOCK(pd->pd_proc); 504 } else 505 sb->st_mode = S_IFREG; 506 sx_sunlock(&proctree_lock); 507 return (0); 508 } 509 510 static int 511 procdesc_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 512 struct thread *td) 513 { 514 515 return (EOPNOTSUPP); 516 } 517 518 static int 519 procdesc_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 520 struct thread *td) 521 { 522 523 return (EOPNOTSUPP); 524 } 525 526 #else /* !PROCDESC */ 527 528 int 529 sys_pdgetpid(struct thread *td, struct pdgetpid_args *uap) 530 { 531 532 return (ENOSYS); 533 } 534 535 #endif /* PROCDESC */ 536