Tue, 17 Nov 2015 09:39:45 -0800
8130910: hsperfdata file is created in wrong directory and not cleaned up if /tmp/hsperfdata_<username> has wrong permissions
Summary: Add check for fchir() failure and disable shared PerfMemory in that case.
Reviewed-by: dcubed, simonis, gthornbr
1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * Copyright 2012, 2013 SAP AG. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
26 #include "precompiled.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "os_aix.inline.hpp"
32 #include "runtime/handles.inline.hpp"
33 #include "runtime/perfMemory.hpp"
34 #include "services/memTracker.hpp"
35 #include "utilities/exceptions.hpp"
37 // put OS-includes here
38 # include <sys/types.h>
39 # include <sys/mman.h>
40 # include <errno.h>
41 # include <stdio.h>
42 # include <unistd.h>
43 # include <sys/stat.h>
44 # include <signal.h>
45 # include <pwd.h>
47 static char* backing_store_file_name = NULL; // name of the backing store
48 // file, if successfully created.
50 // Standard Memory Implementation Details
52 // create the PerfData memory region in standard memory.
53 //
54 static char* create_standard_memory(size_t size) {
56 // allocate an aligned chuck of memory
57 char* mapAddress = os::reserve_memory(size);
59 if (mapAddress == NULL) {
60 return NULL;
61 }
63 // commit memory
64 if (!os::commit_memory(mapAddress, size, !ExecMem)) {
65 if (PrintMiscellaneous && Verbose) {
66 warning("Could not commit PerfData memory\n");
67 }
68 os::release_memory(mapAddress, size);
69 return NULL;
70 }
72 return mapAddress;
73 }
75 // delete the PerfData memory region
76 //
77 static void delete_standard_memory(char* addr, size_t size) {
79 // there are no persistent external resources to cleanup for standard
80 // memory. since DestroyJavaVM does not support unloading of the JVM,
81 // cleanup of the memory resource is not performed. The memory will be
82 // reclaimed by the OS upon termination of the process.
83 //
84 return;
85 }
87 // save the specified memory region to the given file
88 //
89 // Note: this function might be called from signal handler (by os::abort()),
90 // don't allocate heap memory.
91 //
92 static void save_memory_to_file(char* addr, size_t size) {
94 const char* destfile = PerfMemory::get_perfdata_file_path();
95 assert(destfile[0] != '\0', "invalid PerfData file path");
97 int result;
99 RESTARTABLE(::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IREAD|S_IWRITE),
100 result);;
101 if (result == OS_ERR) {
102 if (PrintMiscellaneous && Verbose) {
103 warning("Could not create Perfdata save file: %s: %s\n",
104 destfile, strerror(errno));
105 }
106 } else {
107 int fd = result;
109 for (size_t remaining = size; remaining > 0;) {
111 RESTARTABLE(::write(fd, addr, remaining), result);
112 if (result == OS_ERR) {
113 if (PrintMiscellaneous && Verbose) {
114 warning("Could not write Perfdata save file: %s: %s\n",
115 destfile, strerror(errno));
116 }
117 break;
118 }
120 remaining -= (size_t)result;
121 addr += result;
122 }
124 RESTARTABLE(::close(fd), result);
125 if (PrintMiscellaneous && Verbose) {
126 if (result == OS_ERR) {
127 warning("Could not close %s: %s\n", destfile, strerror(errno));
128 }
129 }
130 }
131 FREE_C_HEAP_ARRAY(char, destfile, mtInternal);
132 }
135 // Shared Memory Implementation Details
137 // Note: the solaris and linux shared memory implementation uses the mmap
138 // interface with a backing store file to implement named shared memory.
139 // Using the file system as the name space for shared memory allows a
140 // common name space to be supported across a variety of platforms. It
141 // also provides a name space that Java applications can deal with through
142 // simple file apis.
143 //
144 // The solaris and linux implementations store the backing store file in
145 // a user specific temporary directory located in the /tmp file system,
146 // which is always a local file system and is sometimes a RAM based file
147 // system.
149 // return the user specific temporary directory name.
150 //
151 // the caller is expected to free the allocated memory.
152 //
153 static char* get_user_tmp_dir(const char* user) {
155 const char* tmpdir = os::get_temp_directory();
156 const char* perfdir = PERFDATA_NAME;
157 size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
158 char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
160 // construct the path name to user specific tmp directory
161 snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
163 return dirname;
164 }
166 // convert the given file name into a process id. if the file
167 // does not meet the file naming constraints, return 0.
168 //
169 static pid_t filename_to_pid(const char* filename) {
171 // a filename that doesn't begin with a digit is not a
172 // candidate for conversion.
173 //
174 if (!isdigit(*filename)) {
175 return 0;
176 }
178 // check if file name can be converted to an integer without
179 // any leftover characters.
180 //
181 char* remainder = NULL;
182 errno = 0;
183 pid_t pid = (pid_t)strtol(filename, &remainder, 10);
185 if (errno != 0) {
186 return 0;
187 }
189 // check for left over characters. If any, then the filename is
190 // not a candidate for conversion.
191 //
192 if (remainder != NULL && *remainder != '\0') {
193 return 0;
194 }
196 // successful conversion, return the pid
197 return pid;
198 }
200 // Check if the given statbuf is considered a secure directory for
201 // the backing store files. Returns true if the directory is considered
202 // a secure location. Returns false if the statbuf is a symbolic link or
203 // if an error occurred.
204 static bool is_statbuf_secure(struct stat *statp) {
205 if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) {
206 // The path represents a link or some non-directory file type,
207 // which is not what we expected. Declare it insecure.
208 //
209 return false;
210 }
211 // We have an existing directory, check if the permissions are safe.
212 if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) {
213 // The directory is open for writing and could be subjected
214 // to a symlink or a hard link attack. Declare it insecure.
215 return false;
216 }
217 // See if the uid of the directory matches the effective uid of the process.
218 //
219 if (statp->st_uid != geteuid()) {
220 // The directory was not created by this user, declare it insecure.
221 return false;
222 }
223 return true;
224 }
227 // Check if the given path is considered a secure directory for
228 // the backing store files. Returns true if the directory exists
229 // and is considered a secure location. Returns false if the path
230 // is a symbolic link or if an error occurred.
231 static bool is_directory_secure(const char* path) {
232 struct stat statbuf;
233 int result = 0;
235 RESTARTABLE(::lstat(path, &statbuf), result);
236 if (result == OS_ERR) {
237 return false;
238 }
240 // The path exists, see if it is secure.
241 return is_statbuf_secure(&statbuf);
242 }
244 // (Taken over from Solaris to support the O_NOFOLLOW case on AIX.)
245 // Check if the given directory file descriptor is considered a secure
246 // directory for the backing store files. Returns true if the directory
247 // exists and is considered a secure location. Returns false if the path
248 // is a symbolic link or if an error occurred.
249 static bool is_dirfd_secure(int dir_fd) {
250 struct stat statbuf;
251 int result = 0;
253 RESTARTABLE(::fstat(dir_fd, &statbuf), result);
254 if (result == OS_ERR) {
255 return false;
256 }
258 // The path exists, now check its mode.
259 return is_statbuf_secure(&statbuf);
260 }
263 // Check to make sure fd1 and fd2 are referencing the same file system object.
264 static bool is_same_fsobject(int fd1, int fd2) {
265 struct stat statbuf1;
266 struct stat statbuf2;
267 int result = 0;
269 RESTARTABLE(::fstat(fd1, &statbuf1), result);
270 if (result == OS_ERR) {
271 return false;
272 }
273 RESTARTABLE(::fstat(fd2, &statbuf2), result);
274 if (result == OS_ERR) {
275 return false;
276 }
278 if ((statbuf1.st_ino == statbuf2.st_ino) &&
279 (statbuf1.st_dev == statbuf2.st_dev)) {
280 return true;
281 } else {
282 return false;
283 }
284 }
286 // Helper functions for open without O_NOFOLLOW which is not present on AIX 5.3/6.1.
287 // We use the jdk6 implementation here.
288 #ifndef O_NOFOLLOW
289 // The O_NOFOLLOW oflag doesn't exist before solaris 5.10, this is to simulate that behaviour
290 // was done in jdk 5/6 hotspot by Oracle this way
291 static int open_o_nofollow_impl(const char* path, int oflag, mode_t mode, bool use_mode) {
292 struct stat orig_st;
293 struct stat new_st;
294 bool create;
295 int error;
296 int fd;
298 create = false;
300 if (lstat(path, &orig_st) != 0) {
301 if (errno == ENOENT && (oflag & O_CREAT) != 0) {
302 // File doesn't exist, but_we want to create it, add O_EXCL flag
303 // to make sure no-one creates it (or a symlink) before us
304 // This works as we expect with symlinks, from posix man page:
305 // 'If O_EXCL and O_CREAT are set, and path names a symbolic
306 // link, open() shall fail and set errno to [EEXIST]'.
307 oflag |= O_EXCL;
308 create = true;
309 } else {
310 // File doesn't exist, and we are not creating it.
311 return OS_ERR;
312 }
313 } else {
314 // Lstat success, check if existing file is a link.
315 if ((orig_st.st_mode & S_IFMT) == S_IFLNK) {
316 // File is a symlink.
317 errno = ELOOP;
318 return OS_ERR;
319 }
320 }
322 if (use_mode == true) {
323 fd = open(path, oflag, mode);
324 } else {
325 fd = open(path, oflag);
326 }
328 if (fd == OS_ERR) {
329 return fd;
330 }
332 // Can't do inode checks on before/after if we created the file.
333 if (create == false) {
334 if (fstat(fd, &new_st) != 0) {
335 // Keep errno from fstat, in case close also fails.
336 error = errno;
337 ::close(fd);
338 errno = error;
339 return OS_ERR;
340 }
342 if (orig_st.st_dev != new_st.st_dev || orig_st.st_ino != new_st.st_ino) {
343 // File was tampered with during race window.
344 ::close(fd);
345 errno = EEXIST;
346 if (PrintMiscellaneous && Verbose) {
347 warning("possible file tampering attempt detected when opening %s", path);
348 }
349 return OS_ERR;
350 }
351 }
353 return fd;
354 }
356 static int open_o_nofollow(const char* path, int oflag, mode_t mode) {
357 return open_o_nofollow_impl(path, oflag, mode, true);
358 }
360 static int open_o_nofollow(const char* path, int oflag) {
361 return open_o_nofollow_impl(path, oflag, 0, false);
362 }
363 #endif
365 // Open the directory of the given path and validate it.
366 // Return a DIR * of the open directory.
367 static DIR *open_directory_secure(const char* dirname) {
368 // Open the directory using open() so that it can be verified
369 // to be secure by calling is_dirfd_secure(), opendir() and then check
370 // to see if they are the same file system object. This method does not
371 // introduce a window of opportunity for the directory to be attacked that
372 // calling opendir() and is_directory_secure() does.
373 int result;
374 DIR *dirp = NULL;
376 // No O_NOFOLLOW defined at buildtime, and it is not documented for open;
377 // so provide a workaround in this case.
378 #ifdef O_NOFOLLOW
379 RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result);
380 #else
381 // workaround (jdk6 coding)
382 RESTARTABLE(::open_o_nofollow(dirname, O_RDONLY), result);
383 #endif
385 if (result == OS_ERR) {
386 // Directory doesn't exist or is a symlink, so there is nothing to cleanup.
387 if (PrintMiscellaneous && Verbose) {
388 if (errno == ELOOP) {
389 warning("directory %s is a symlink and is not secure\n", dirname);
390 } else {
391 warning("could not open directory %s: %s\n", dirname, strerror(errno));
392 }
393 }
394 return dirp;
395 }
396 int fd = result;
398 // Determine if the open directory is secure.
399 if (!is_dirfd_secure(fd)) {
400 // The directory is not a secure directory.
401 os::close(fd);
402 return dirp;
403 }
405 // Open the directory.
406 dirp = ::opendir(dirname);
407 if (dirp == NULL) {
408 // The directory doesn't exist, close fd and return.
409 os::close(fd);
410 return dirp;
411 }
413 // Check to make sure fd and dirp are referencing the same file system object.
414 if (!is_same_fsobject(fd, dirp->dd_fd)) {
415 // The directory is not secure.
416 os::close(fd);
417 os::closedir(dirp);
418 dirp = NULL;
419 return dirp;
420 }
422 // Close initial open now that we know directory is secure
423 os::close(fd);
425 return dirp;
426 }
428 // NOTE: The code below uses fchdir(), open() and unlink() because
429 // fdopendir(), openat() and unlinkat() are not supported on all
430 // versions. Once the support for fdopendir(), openat() and unlinkat()
431 // is available on all supported versions the code can be changed
432 // to use these functions.
434 // Open the directory of the given path, validate it and set the
435 // current working directory to it.
436 // Return a DIR * of the open directory and the saved cwd fd.
437 //
438 static DIR *open_directory_secure_cwd(const char* dirname, int *saved_cwd_fd) {
440 // Open the directory.
441 DIR* dirp = open_directory_secure(dirname);
442 if (dirp == NULL) {
443 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
444 return dirp;
445 }
446 int fd = dirp->dd_fd;
448 // Open a fd to the cwd and save it off.
449 int result;
450 RESTARTABLE(::open(".", O_RDONLY), result);
451 if (result == OS_ERR) {
452 *saved_cwd_fd = -1;
453 } else {
454 *saved_cwd_fd = result;
455 }
457 // Set the current directory to dirname by using the fd of the directory and
458 // handle errors, otherwise shared memory files will be created in cwd.
459 result = fchdir(fd);
460 if (result == OS_ERR) {
461 if (PrintMiscellaneous && Verbose) {
462 warning("could not change to directory %s", dirname);
463 }
464 if (*saved_cwd_fd != -1) {
465 ::close(*saved_cwd_fd);
466 *saved_cwd_fd = -1;
467 }
468 // Close the directory.
469 os::closedir(dirp);
470 return NULL;
471 } else {
472 return dirp;
473 }
474 }
476 // Close the directory and restore the current working directory.
477 //
478 static void close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
480 int result;
481 // If we have a saved cwd change back to it and close the fd.
482 if (saved_cwd_fd != -1) {
483 result = fchdir(saved_cwd_fd);
484 ::close(saved_cwd_fd);
485 }
487 // Close the directory.
488 os::closedir(dirp);
489 }
491 // Check if the given file descriptor is considered a secure.
492 static bool is_file_secure(int fd, const char *filename) {
494 int result;
495 struct stat statbuf;
497 // Determine if the file is secure.
498 RESTARTABLE(::fstat(fd, &statbuf), result);
499 if (result == OS_ERR) {
500 if (PrintMiscellaneous && Verbose) {
501 warning("fstat failed on %s: %s\n", filename, strerror(errno));
502 }
503 return false;
504 }
505 if (statbuf.st_nlink > 1) {
506 // A file with multiple links is not expected.
507 if (PrintMiscellaneous && Verbose) {
508 warning("file %s has multiple links\n", filename);
509 }
510 return false;
511 }
512 return true;
513 }
515 // Return the user name for the given user id.
516 //
517 // The caller is expected to free the allocated memory.
518 static char* get_user_name(uid_t uid) {
520 struct passwd pwent;
522 // Determine the max pwbuf size from sysconf, and hardcode
523 // a default if this not available through sysconf.
524 long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
525 if (bufsize == -1)
526 bufsize = 1024;
528 char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
530 // POSIX interface to getpwuid_r is used on LINUX
531 struct passwd* p;
532 int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
534 if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') {
535 if (PrintMiscellaneous && Verbose) {
536 if (result != 0) {
537 warning("Could not retrieve passwd entry: %s\n",
538 strerror(result));
539 }
540 else if (p == NULL) {
541 // this check is added to protect against an observed problem
542 // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0,
543 // indicating success, but has p == NULL. This was observed when
544 // inserting a file descriptor exhaustion fault prior to the call
545 // getpwuid_r() call. In this case, error is set to the appropriate
546 // error condition, but this is undocumented behavior. This check
547 // is safe under any condition, but the use of errno in the output
548 // message may result in an erroneous message.
549 // Bug Id 89052 was opened with RedHat.
550 //
551 warning("Could not retrieve passwd entry: %s\n",
552 strerror(errno));
553 }
554 else {
555 warning("Could not determine user name: %s\n",
556 p->pw_name == NULL ? "pw_name = NULL" :
557 "pw_name zero length");
558 }
559 }
560 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
561 return NULL;
562 }
564 char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
565 strcpy(user_name, p->pw_name);
567 FREE_C_HEAP_ARRAY(char, pwbuf, mtInternal);
568 return user_name;
569 }
571 // return the name of the user that owns the process identified by vmid.
572 //
573 // This method uses a slow directory search algorithm to find the backing
574 // store file for the specified vmid and returns the user name, as determined
575 // by the user name suffix of the hsperfdata_<username> directory name.
576 //
577 // the caller is expected to free the allocated memory.
578 //
579 static char* get_user_name_slow(int vmid, TRAPS) {
581 // short circuit the directory search if the process doesn't even exist.
582 if (kill(vmid, 0) == OS_ERR) {
583 if (errno == ESRCH) {
584 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
585 "Process not found");
586 }
587 else /* EPERM */ {
588 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
589 }
590 }
592 // directory search
593 char* oldest_user = NULL;
594 time_t oldest_ctime = 0;
596 const char* tmpdirname = os::get_temp_directory();
598 DIR* tmpdirp = os::opendir(tmpdirname);
600 if (tmpdirp == NULL) {
601 return NULL;
602 }
604 // for each entry in the directory that matches the pattern hsperfdata_*,
605 // open the directory and check if the file for the given vmid exists.
606 // The file with the expected name and the latest creation date is used
607 // to determine the user name for the process id.
608 //
609 struct dirent* dentry;
610 char* tdbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(tmpdirname), mtInternal);
611 errno = 0;
612 while ((dentry = os::readdir(tmpdirp, (struct dirent *)tdbuf)) != NULL) {
614 // check if the directory entry is a hsperfdata file
615 if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) {
616 continue;
617 }
619 char* usrdir_name = NEW_C_HEAP_ARRAY(char,
620 strlen(tmpdirname) + strlen(dentry->d_name) + 2, mtInternal);
621 strcpy(usrdir_name, tmpdirname);
622 strcat(usrdir_name, "/");
623 strcat(usrdir_name, dentry->d_name);
625 // Open the user directory.
626 DIR* subdirp = open_directory_secure(usrdir_name);
628 if (subdirp == NULL) {
629 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
630 continue;
631 }
633 // Since we don't create the backing store files in directories
634 // pointed to by symbolic links, we also don't follow them when
635 // looking for the files. We check for a symbolic link after the
636 // call to opendir in order to eliminate a small window where the
637 // symlink can be exploited.
638 //
639 if (!is_directory_secure(usrdir_name)) {
640 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
641 os::closedir(subdirp);
642 continue;
643 }
645 struct dirent* udentry;
646 char* udbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(usrdir_name), mtInternal);
647 errno = 0;
648 while ((udentry = os::readdir(subdirp, (struct dirent *)udbuf)) != NULL) {
650 if (filename_to_pid(udentry->d_name) == vmid) {
651 struct stat statbuf;
652 int result;
654 char* filename = NEW_C_HEAP_ARRAY(char,
655 strlen(usrdir_name) + strlen(udentry->d_name) + 2, mtInternal);
657 strcpy(filename, usrdir_name);
658 strcat(filename, "/");
659 strcat(filename, udentry->d_name);
661 // don't follow symbolic links for the file
662 RESTARTABLE(::lstat(filename, &statbuf), result);
663 if (result == OS_ERR) {
664 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
665 continue;
666 }
668 // skip over files that are not regular files.
669 if (!S_ISREG(statbuf.st_mode)) {
670 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
671 continue;
672 }
674 // compare and save filename with latest creation time
675 if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
677 if (statbuf.st_ctime > oldest_ctime) {
678 char* user = strchr(dentry->d_name, '_') + 1;
680 if (oldest_user != NULL) FREE_C_HEAP_ARRAY(char, oldest_user, mtInternal);
681 oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
683 strcpy(oldest_user, user);
684 oldest_ctime = statbuf.st_ctime;
685 }
686 }
688 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
689 }
690 }
691 os::closedir(subdirp);
692 FREE_C_HEAP_ARRAY(char, udbuf, mtInternal);
693 FREE_C_HEAP_ARRAY(char, usrdir_name, mtInternal);
694 }
695 os::closedir(tmpdirp);
696 FREE_C_HEAP_ARRAY(char, tdbuf, mtInternal);
698 return(oldest_user);
699 }
701 // return the name of the user that owns the JVM indicated by the given vmid.
702 //
703 static char* get_user_name(int vmid, TRAPS) {
704 return get_user_name_slow(vmid, CHECK_NULL);
705 }
707 // return the file name of the backing store file for the named
708 // shared memory region for the given user name and vmid.
709 //
710 // the caller is expected to free the allocated memory.
711 //
712 static char* get_sharedmem_filename(const char* dirname, int vmid) {
714 // add 2 for the file separator and a null terminator.
715 size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
717 char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
718 snprintf(name, nbytes, "%s/%d", dirname, vmid);
720 return name;
721 }
724 // remove file
725 //
726 // this method removes the file specified by the given path
727 //
728 static void remove_file(const char* path) {
730 int result;
732 // if the file is a directory, the following unlink will fail. since
733 // we don't expect to find directories in the user temp directory, we
734 // won't try to handle this situation. even if accidentially or
735 // maliciously planted, the directory's presence won't hurt anything.
736 //
737 RESTARTABLE(::unlink(path), result);
738 if (PrintMiscellaneous && Verbose && result == OS_ERR) {
739 if (errno != ENOENT) {
740 warning("Could not unlink shared memory backing"
741 " store file %s : %s\n", path, strerror(errno));
742 }
743 }
744 }
746 // Cleanup stale shared memory resources
747 //
748 // This method attempts to remove all stale shared memory files in
749 // the named user temporary directory. It scans the named directory
750 // for files matching the pattern ^$[0-9]*$. For each file found, the
751 // process id is extracted from the file name and a test is run to
752 // determine if the process is alive. If the process is not alive,
753 // any stale file resources are removed.
754 static void cleanup_sharedmem_resources(const char* dirname) {
756 int saved_cwd_fd;
757 // Open the directory.
758 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
759 if (dirp == NULL) {
760 // Directory doesn't exist or is insecure, so there is nothing to cleanup.
761 return;
762 }
764 // For each entry in the directory that matches the expected file
765 // name pattern, determine if the file resources are stale and if
766 // so, remove the file resources. Note, instrumented HotSpot processes
767 // for this user may start and/or terminate during this search and
768 // remove or create new files in this directory. The behavior of this
769 // loop under these conditions is dependent upon the implementation of
770 // opendir/readdir.
771 struct dirent* entry;
772 char* dbuf = NEW_C_HEAP_ARRAY(char, os::readdir_buf_size(dirname), mtInternal);
774 errno = 0;
775 while ((entry = os::readdir(dirp, (struct dirent *)dbuf)) != NULL) {
777 pid_t pid = filename_to_pid(entry->d_name);
779 if (pid == 0) {
781 if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0) {
783 // Attempt to remove all unexpected files, except "." and "..".
784 unlink(entry->d_name);
785 }
787 errno = 0;
788 continue;
789 }
791 // We now have a file name that converts to a valid integer
792 // that could represent a process id . if this process id
793 // matches the current process id or the process is not running,
794 // then remove the stale file resources.
795 //
796 // Process liveness is detected by sending signal number 0 to
797 // the process id (see kill(2)). if kill determines that the
798 // process does not exist, then the file resources are removed.
799 // if kill determines that that we don't have permission to
800 // signal the process, then the file resources are assumed to
801 // be stale and are removed because the resources for such a
802 // process should be in a different user specific directory.
803 if ((pid == os::current_process_id()) ||
804 (kill(pid, 0) == OS_ERR && (errno == ESRCH || errno == EPERM))) {
806 unlink(entry->d_name);
807 }
808 errno = 0;
809 }
811 // Close the directory and reset the current working directory.
812 close_directory_secure_cwd(dirp, saved_cwd_fd);
814 FREE_C_HEAP_ARRAY(char, dbuf, mtInternal);
815 }
817 // Make the user specific temporary directory. Returns true if
818 // the directory exists and is secure upon return. Returns false
819 // if the directory exists but is either a symlink, is otherwise
820 // insecure, or if an error occurred.
821 static bool make_user_tmp_dir(const char* dirname) {
823 // Create the directory with 0755 permissions. note that the directory
824 // will be owned by euid::egid, which may not be the same as uid::gid.
825 if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) {
826 if (errno == EEXIST) {
827 // The directory already exists and was probably created by another
828 // JVM instance. However, this could also be the result of a
829 // deliberate symlink. Verify that the existing directory is safe.
830 if (!is_directory_secure(dirname)) {
831 // Directory is not secure.
832 if (PrintMiscellaneous && Verbose) {
833 warning("%s directory is insecure\n", dirname);
834 }
835 return false;
836 }
837 }
838 else {
839 // we encountered some other failure while attempting
840 // to create the directory
841 //
842 if (PrintMiscellaneous && Verbose) {
843 warning("could not create directory %s: %s\n",
844 dirname, strerror(errno));
845 }
846 return false;
847 }
848 }
849 return true;
850 }
852 // create the shared memory file resources
853 //
854 // This method creates the shared memory file with the given size
855 // This method also creates the user specific temporary directory, if
856 // it does not yet exist.
857 //
858 static int create_sharedmem_resources(const char* dirname, const char* filename, size_t size) {
860 // make the user temporary directory
861 if (!make_user_tmp_dir(dirname)) {
862 // could not make/find the directory or the found directory
863 // was not secure
864 return -1;
865 }
867 int saved_cwd_fd;
868 // Open the directory and set the current working directory to it.
869 DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd);
870 if (dirp == NULL) {
871 // Directory doesn't exist or is insecure, so cannot create shared
872 // memory file.
873 return -1;
874 }
876 // Open the filename in the current directory.
877 // Cannot use O_TRUNC here; truncation of an existing file has to happen
878 // after the is_file_secure() check below.
879 int result;
881 // No O_NOFOLLOW defined at buildtime, and it is not documented for open;
882 // so provide a workaround in this case.
883 #ifdef O_NOFOLLOW
884 RESTARTABLE(::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IREAD|S_IWRITE), result);
885 #else
886 // workaround function (jdk6 code)
887 RESTARTABLE(::open_o_nofollow(filename, O_RDWR|O_CREAT, S_IREAD|S_IWRITE), result);
888 #endif
890 if (result == OS_ERR) {
891 if (PrintMiscellaneous && Verbose) {
892 if (errno == ELOOP) {
893 warning("file %s is a symlink and is not secure\n", filename);
894 } else {
895 warning("could not create file %s: %s\n", filename, strerror(errno));
896 }
897 }
898 // Close the directory and reset the current working directory.
899 close_directory_secure_cwd(dirp, saved_cwd_fd);
901 return -1;
902 }
903 // Close the directory and reset the current working directory.
904 close_directory_secure_cwd(dirp, saved_cwd_fd);
906 // save the file descriptor
907 int fd = result;
909 // Check to see if the file is secure.
910 if (!is_file_secure(fd, filename)) {
911 ::close(fd);
912 return -1;
913 }
915 // Truncate the file to get rid of any existing data.
916 RESTARTABLE(::ftruncate(fd, (off_t)0), result);
917 if (result == OS_ERR) {
918 if (PrintMiscellaneous && Verbose) {
919 warning("could not truncate shared memory file: %s\n", strerror(errno));
920 }
921 ::close(fd);
922 return -1;
923 }
924 // set the file size
925 RESTARTABLE(::ftruncate(fd, (off_t)size), result);
926 if (result == OS_ERR) {
927 if (PrintMiscellaneous && Verbose) {
928 warning("could not set shared memory file size: %s\n", strerror(errno));
929 }
930 RESTARTABLE(::close(fd), result);
931 return -1;
932 }
934 return fd;
935 }
937 // open the shared memory file for the given user and vmid. returns
938 // the file descriptor for the open file or -1 if the file could not
939 // be opened.
940 //
941 static int open_sharedmem_file(const char* filename, int oflags, TRAPS) {
943 // open the file
944 int result;
945 // No O_NOFOLLOW defined at buildtime, and it is not documented for open;
946 // so provide a workaround in this case
947 #ifdef O_NOFOLLOW
948 RESTARTABLE(::open(filename, oflags), result);
949 #else
950 RESTARTABLE(::open_o_nofollow(filename, oflags), result);
951 #endif
953 if (result == OS_ERR) {
954 if (errno == ENOENT) {
955 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
956 "Process not found");
957 }
958 else if (errno == EACCES) {
959 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(),
960 "Permission denied");
961 }
962 else {
963 THROW_MSG_0(vmSymbols::java_io_IOException(), strerror(errno));
964 }
965 }
966 int fd = result;
968 // Check to see if the file is secure.
969 if (!is_file_secure(fd, filename)) {
970 ::close(fd);
971 return -1;
972 }
974 return fd;
975 }
977 // create a named shared memory region. returns the address of the
978 // memory region on success or NULL on failure. A return value of
979 // NULL will ultimately disable the shared memory feature.
980 //
981 // On Solaris and Linux, the name space for shared memory objects
982 // is the file system name space.
983 //
984 // A monitoring application attaching to a JVM does not need to know
985 // the file system name of the shared memory object. However, it may
986 // be convenient for applications to discover the existence of newly
987 // created and terminating JVMs by watching the file system name space
988 // for files being created or removed.
989 //
990 static char* mmap_create_shared(size_t size) {
992 int result;
993 int fd;
994 char* mapAddress;
996 int vmid = os::current_process_id();
998 char* user_name = get_user_name(geteuid());
1000 if (user_name == NULL)
1001 return NULL;
1003 char* dirname = get_user_tmp_dir(user_name);
1004 char* filename = get_sharedmem_filename(dirname, vmid);
1006 // Get the short filename.
1007 char* short_filename = strrchr(filename, '/');
1008 if (short_filename == NULL) {
1009 short_filename = filename;
1010 } else {
1011 short_filename++;
1012 }
1014 // cleanup any stale shared memory files
1015 cleanup_sharedmem_resources(dirname);
1017 assert(((size > 0) && (size % os::vm_page_size() == 0)),
1018 "unexpected PerfMemory region size");
1020 fd = create_sharedmem_resources(dirname, short_filename, size);
1022 FREE_C_HEAP_ARRAY(char, user_name, mtInternal);
1023 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1025 if (fd == -1) {
1026 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1027 return NULL;
1028 }
1030 mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
1032 // attempt to close the file - restart it if it was interrupted,
1033 // but ignore other failures
1034 RESTARTABLE(::close(fd), result);
1035 assert(result != OS_ERR, "could not close file");
1037 if (mapAddress == MAP_FAILED) {
1038 if (PrintMiscellaneous && Verbose) {
1039 warning("mmap failed - %s\n", strerror(errno));
1040 }
1041 remove_file(filename);
1042 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1043 return NULL;
1044 }
1046 // save the file name for use in delete_shared_memory()
1047 backing_store_file_name = filename;
1049 // clear the shared memory region
1050 (void)::memset((void*) mapAddress, 0, size);
1052 // It does not go through os api, the operation has to record from here.
1053 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, CURRENT_PC, mtInternal);
1055 return mapAddress;
1056 }
1058 // release a named shared memory region
1059 //
1060 static void unmap_shared(char* addr, size_t bytes) {
1061 // Do not rely on os::reserve_memory/os::release_memory to use mmap.
1062 // Use os::reserve_memory/os::release_memory for PerfDisableSharedMem=1, mmap/munmap for PerfDisableSharedMem=0
1063 if (::munmap(addr, bytes) == -1) {
1064 warning("perfmemory: munmap failed (%d)\n", errno);
1065 }
1066 }
1068 // create the PerfData memory region in shared memory.
1069 //
1070 static char* create_shared_memory(size_t size) {
1072 // create the shared memory region.
1073 return mmap_create_shared(size);
1074 }
1076 // delete the shared PerfData memory region
1077 //
1078 static void delete_shared_memory(char* addr, size_t size) {
1080 // cleanup the persistent shared memory resources. since DestroyJavaVM does
1081 // not support unloading of the JVM, unmapping of the memory resource is
1082 // not performed. The memory will be reclaimed by the OS upon termination of
1083 // the process. The backing store file is deleted from the file system.
1085 assert(!PerfDisableSharedMem, "shouldn't be here");
1087 if (backing_store_file_name != NULL) {
1088 remove_file(backing_store_file_name);
1089 // Don't.. Free heap memory could deadlock os::abort() if it is called
1090 // from signal handler. OS will reclaim the heap memory.
1091 // FREE_C_HEAP_ARRAY(char, backing_store_file_name, mtInternal);
1092 backing_store_file_name = NULL;
1093 }
1094 }
1096 // return the size of the file for the given file descriptor
1097 // or 0 if it is not a valid size for a shared memory file
1098 //
1099 static size_t sharedmem_filesize(int fd, TRAPS) {
1101 struct stat statbuf;
1102 int result;
1104 RESTARTABLE(::fstat(fd, &statbuf), result);
1105 if (result == OS_ERR) {
1106 if (PrintMiscellaneous && Verbose) {
1107 warning("fstat failed: %s\n", strerror(errno));
1108 }
1109 THROW_MSG_0(vmSymbols::java_io_IOException(),
1110 "Could not determine PerfMemory size");
1111 }
1113 if ((statbuf.st_size == 0) ||
1114 ((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
1115 THROW_MSG_0(vmSymbols::java_lang_Exception(),
1116 "Invalid PerfMemory size");
1117 }
1119 return (size_t)statbuf.st_size;
1120 }
1122 // attach to a named shared memory region.
1123 //
1124 static void mmap_attach_shared(const char* user, int vmid, PerfMemory::PerfMemoryMode mode, char** addr, size_t* sizep, TRAPS) {
1126 char* mapAddress;
1127 int result;
1128 int fd;
1129 size_t size = 0;
1130 const char* luser = NULL;
1132 int mmap_prot;
1133 int file_flags;
1135 ResourceMark rm;
1137 // map the high level access mode to the appropriate permission
1138 // constructs for the file and the shared memory mapping.
1139 if (mode == PerfMemory::PERF_MODE_RO) {
1140 mmap_prot = PROT_READ;
1142 // No O_NOFOLLOW defined at buildtime, and it is not documented for open.
1143 #ifdef O_NOFOLLOW
1144 file_flags = O_RDONLY | O_NOFOLLOW;
1145 #else
1146 file_flags = O_RDONLY;
1147 #endif
1148 }
1149 else if (mode == PerfMemory::PERF_MODE_RW) {
1150 #ifdef LATER
1151 mmap_prot = PROT_READ | PROT_WRITE;
1152 file_flags = O_RDWR | O_NOFOLLOW;
1153 #else
1154 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1155 "Unsupported access mode");
1156 #endif
1157 }
1158 else {
1159 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1160 "Illegal access mode");
1161 }
1163 if (user == NULL || strlen(user) == 0) {
1164 luser = get_user_name(vmid, CHECK);
1165 }
1166 else {
1167 luser = user;
1168 }
1170 if (luser == NULL) {
1171 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1172 "Could not map vmid to user Name");
1173 }
1175 char* dirname = get_user_tmp_dir(luser);
1177 // since we don't follow symbolic links when creating the backing
1178 // store file, we don't follow them when attaching either.
1179 //
1180 if (!is_directory_secure(dirname)) {
1181 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1182 if (luser != user) {
1183 FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1184 }
1185 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
1186 "Process not found");
1187 }
1189 char* filename = get_sharedmem_filename(dirname, vmid);
1191 // copy heap memory to resource memory. the open_sharedmem_file
1192 // method below need to use the filename, but could throw an
1193 // exception. using a resource array prevents the leak that
1194 // would otherwise occur.
1195 char* rfilename = NEW_RESOURCE_ARRAY(char, strlen(filename) + 1);
1196 strcpy(rfilename, filename);
1198 // free the c heap resources that are no longer needed
1199 if (luser != user) FREE_C_HEAP_ARRAY(char, luser, mtInternal);
1200 FREE_C_HEAP_ARRAY(char, dirname, mtInternal);
1201 FREE_C_HEAP_ARRAY(char, filename, mtInternal);
1203 // open the shared memory file for the give vmid
1204 fd = open_sharedmem_file(rfilename, file_flags, CHECK);
1205 assert(fd != OS_ERR, "unexpected value");
1207 if (*sizep == 0) {
1208 size = sharedmem_filesize(fd, CHECK);
1209 assert(size != 0, "unexpected size");
1210 } else {
1211 size = *sizep;
1212 }
1214 mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
1216 // attempt to close the file - restart if it gets interrupted,
1217 // but ignore other failures
1218 RESTARTABLE(::close(fd), result);
1219 assert(result != OS_ERR, "could not close file");
1221 if (mapAddress == MAP_FAILED) {
1222 if (PrintMiscellaneous && Verbose) {
1223 warning("mmap failed: %s\n", strerror(errno));
1224 }
1225 THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
1226 "Could not map PerfMemory");
1227 }
1229 // It does not go through os api, the operation has to record from here.
1230 MemTracker::record_virtual_memory_reserve((address)mapAddress, size, CURRENT_PC, mtInternal);
1232 *addr = mapAddress;
1233 *sizep = size;
1235 if (PerfTraceMemOps) {
1236 tty->print("mapped " SIZE_FORMAT " bytes for vmid %d at "
1237 INTPTR_FORMAT "\n", size, vmid, (void*)mapAddress);
1238 }
1239 }
1244 // create the PerfData memory region
1245 //
1246 // This method creates the memory region used to store performance
1247 // data for the JVM. The memory may be created in standard or
1248 // shared memory.
1249 //
1250 void PerfMemory::create_memory_region(size_t size) {
1252 if (PerfDisableSharedMem) {
1253 // do not share the memory for the performance data.
1254 _start = create_standard_memory(size);
1255 }
1256 else {
1257 _start = create_shared_memory(size);
1258 if (_start == NULL) {
1260 // creation of the shared memory region failed, attempt
1261 // to create a contiguous, non-shared memory region instead.
1262 //
1263 if (PrintMiscellaneous && Verbose) {
1264 warning("Reverting to non-shared PerfMemory region.\n");
1265 }
1266 PerfDisableSharedMem = true;
1267 _start = create_standard_memory(size);
1268 }
1269 }
1271 if (_start != NULL) _capacity = size;
1273 }
1275 // delete the PerfData memory region
1276 //
1277 // This method deletes the memory region used to store performance
1278 // data for the JVM. The memory region indicated by the <address, size>
1279 // tuple will be inaccessible after a call to this method.
1280 //
1281 void PerfMemory::delete_memory_region() {
1283 assert((start() != NULL && capacity() > 0), "verify proper state");
1285 // If user specifies PerfDataSaveFile, it will save the performance data
1286 // to the specified file name no matter whether PerfDataSaveToFile is specified
1287 // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag
1288 // -XX:+PerfDataSaveToFile.
1289 if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
1290 save_memory_to_file(start(), capacity());
1291 }
1293 if (PerfDisableSharedMem) {
1294 delete_standard_memory(start(), capacity());
1295 }
1296 else {
1297 delete_shared_memory(start(), capacity());
1298 }
1299 }
1301 // attach to the PerfData memory region for another JVM
1302 //
1303 // This method returns an <address, size> tuple that points to
1304 // a memory buffer that is kept reasonably synchronized with
1305 // the PerfData memory region for the indicated JVM. This
1306 // buffer may be kept in synchronization via shared memory
1307 // or some other mechanism that keeps the buffer updated.
1308 //
1309 // If the JVM chooses not to support the attachability feature,
1310 // this method should throw an UnsupportedOperation exception.
1311 //
1312 // This implementation utilizes named shared memory to map
1313 // the indicated process's PerfData memory region into this JVMs
1314 // address space.
1315 //
1316 void PerfMemory::attach(const char* user, int vmid, PerfMemoryMode mode, char** addrp, size_t* sizep, TRAPS) {
1318 if (vmid == 0 || vmid == os::current_process_id()) {
1319 *addrp = start();
1320 *sizep = capacity();
1321 return;
1322 }
1324 mmap_attach_shared(user, vmid, mode, addrp, sizep, CHECK);
1325 }
1327 // detach from the PerfData memory region of another JVM
1328 //
1329 // This method detaches the PerfData memory region of another
1330 // JVM, specified as an <address, size> tuple of a buffer
1331 // in this process's address space. This method may perform
1332 // arbitrary actions to accomplish the detachment. The memory
1333 // region specified by <address, size> will be inaccessible after
1334 // a call to this method.
1335 //
1336 // If the JVM chooses not to support the attachability feature,
1337 // this method should throw an UnsupportedOperation exception.
1338 //
1339 // This implementation utilizes named shared memory to detach
1340 // the indicated process's PerfData memory region from this
1341 // process's address space.
1342 //
1343 void PerfMemory::detach(char* addr, size_t bytes, TRAPS) {
1345 assert(addr != 0, "address sanity check");
1346 assert(bytes > 0, "capacity sanity check");
1348 if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) {
1349 // prevent accidental detachment of this process's PerfMemory region
1350 return;
1351 }
1353 unmap_shared(addr, bytes);
1354 }
1356 char* PerfMemory::backing_store_filename() {
1357 return backing_store_file_name;
1358 }