1 /*
2 * Copyright (c) 2011, Comtrol Corp.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29 #include "defs.h"
30 #include <sys/param.h>
31 #include <poll.h>
32
33 #include "syscall.h"
34
35 const char **paths_selected = NULL;
36 static unsigned num_selected = 0;
37
38 /*
39 * Return true if specified path matches one that we're tracing.
40 */
41 static int
pathmatch(const char * path)42 pathmatch(const char *path)
43 {
44 unsigned i;
45
46 for (i = 0; i < num_selected; ++i) {
47 if (strcmp(path, paths_selected[i]) == 0)
48 return 1;
49 }
50 return 0;
51 }
52
53 /*
54 * Return true if specified path (in user-space) matches.
55 */
56 static int
upathmatch(struct tcb * const tcp,const kernel_ulong_t upath)57 upathmatch(struct tcb *const tcp, const kernel_ulong_t upath)
58 {
59 char path[PATH_MAX + 1];
60
61 return umovestr(tcp, upath, sizeof path, path) > 0 &&
62 pathmatch(path);
63 }
64
65 /*
66 * Return true if specified fd maps to a path we're tracing.
67 */
68 static int
fdmatch(struct tcb * tcp,int fd)69 fdmatch(struct tcb *tcp, int fd)
70 {
71 char path[PATH_MAX + 1];
72 int n = getfdpath(tcp, fd, path, sizeof(path));
73
74 return n >= 0 && pathmatch(path);
75 }
76
77 /*
78 * Add a path to the set we're tracing.
79 * Specifying NULL will delete all paths.
80 */
81 static void
storepath(const char * path)82 storepath(const char *path)
83 {
84 unsigned i;
85
86 if (pathmatch(path))
87 return; /* already in table */
88
89 i = num_selected++;
90 paths_selected = xreallocarray(paths_selected, num_selected,
91 sizeof(paths_selected[0]));
92 paths_selected[i] = path;
93 }
94
95 /*
96 * Get path associated with fd.
97 */
98 int
getfdpath(struct tcb * tcp,int fd,char * buf,unsigned bufsize)99 getfdpath(struct tcb *tcp, int fd, char *buf, unsigned bufsize)
100 {
101 char linkpath[sizeof("/proc/%u/fd/%u") + 2 * sizeof(int)*3];
102 ssize_t n;
103
104 if (fd < 0)
105 return -1;
106
107 sprintf(linkpath, "/proc/%u/fd/%u", tcp->pid, fd);
108 n = readlink(linkpath, buf, bufsize - 1);
109 /*
110 * NB: if buf is too small, readlink doesn't fail,
111 * it returns truncated result (IOW: n == bufsize - 1).
112 */
113 if (n >= 0)
114 buf[n] = '\0';
115 return n;
116 }
117
118 /*
119 * Add a path to the set we're tracing. Also add the canonicalized
120 * version of the path. Secifying NULL will delete all paths.
121 */
122 void
pathtrace_select(const char * path)123 pathtrace_select(const char *path)
124 {
125 char *rpath;
126
127 storepath(path);
128
129 rpath = realpath(path, NULL);
130
131 if (rpath == NULL)
132 return;
133
134 /* if realpath and specified path are same, we're done */
135 if (strcmp(path, rpath) == 0) {
136 free(rpath);
137 return;
138 }
139
140 error_msg("Requested path '%s' resolved into '%s'", path, rpath);
141 storepath(rpath);
142 }
143
144 /*
145 * Return true if syscall accesses a selected path
146 * (or if no paths have been specified for tracing).
147 */
148 int
pathtrace_match(struct tcb * tcp)149 pathtrace_match(struct tcb *tcp)
150 {
151 const struct_sysent *s;
152
153 s = tcp->s_ent;
154
155 if (!(s->sys_flags & (TRACE_FILE | TRACE_DESC | TRACE_NETWORK)))
156 return 0;
157
158 /*
159 * Check for special cases where we need to do something
160 * other than test arg[0].
161 */
162
163 switch (s->sen) {
164 case SEN_dup2:
165 case SEN_dup3:
166 case SEN_kexec_file_load:
167 case SEN_sendfile:
168 case SEN_sendfile64:
169 case SEN_tee:
170 /* fd, fd */
171 return fdmatch(tcp, tcp->u_arg[0]) ||
172 fdmatch(tcp, tcp->u_arg[1]);
173
174 case SEN_faccessat:
175 case SEN_fchmodat:
176 case SEN_fchownat:
177 case SEN_fstatat64:
178 case SEN_futimesat:
179 case SEN_inotify_add_watch:
180 case SEN_mkdirat:
181 case SEN_mknodat:
182 case SEN_name_to_handle_at:
183 case SEN_newfstatat:
184 case SEN_openat:
185 case SEN_readlinkat:
186 case SEN_unlinkat:
187 case SEN_utimensat:
188 /* fd, path */
189 return fdmatch(tcp, tcp->u_arg[0]) ||
190 upathmatch(tcp, tcp->u_arg[1]);
191
192 case SEN_link:
193 case SEN_mount:
194 case SEN_pivotroot:
195 /* path, path */
196 return upathmatch(tcp, tcp->u_arg[0]) ||
197 upathmatch(tcp, tcp->u_arg[1]);
198
199 case SEN_quotactl:
200 /* x, path */
201 return upathmatch(tcp, tcp->u_arg[1]);
202
203 case SEN_linkat:
204 case SEN_renameat2:
205 case SEN_renameat:
206 /* fd, path, fd, path */
207 return fdmatch(tcp, tcp->u_arg[0]) ||
208 fdmatch(tcp, tcp->u_arg[2]) ||
209 upathmatch(tcp, tcp->u_arg[1]) ||
210 upathmatch(tcp, tcp->u_arg[3]);
211
212 case SEN_old_mmap:
213 #if defined(S390)
214 case SEN_old_mmap_pgoff:
215 #endif
216 case SEN_mmap:
217 case SEN_mmap_4koff:
218 case SEN_mmap_pgoff:
219 case SEN_ARCH_mmap:
220 /* x, x, x, x, fd */
221 return fdmatch(tcp, tcp->u_arg[4]);
222
223 case SEN_symlinkat:
224 /* path, fd, path */
225 return fdmatch(tcp, tcp->u_arg[1]) ||
226 upathmatch(tcp, tcp->u_arg[0]) ||
227 upathmatch(tcp, tcp->u_arg[2]);
228
229 case SEN_copy_file_range:
230 case SEN_splice:
231 /* fd, x, fd, x, x, x */
232 return fdmatch(tcp, tcp->u_arg[0]) ||
233 fdmatch(tcp, tcp->u_arg[2]);
234
235 case SEN_epoll_ctl:
236 /* x, x, fd, x */
237 return fdmatch(tcp, tcp->u_arg[2]);
238
239
240 case SEN_fanotify_mark:
241 /* x, x, x, fd, path */
242 return fdmatch(tcp, tcp->u_arg[3]) ||
243 upathmatch(tcp, tcp->u_arg[4]);
244
245 case SEN_oldselect:
246 case SEN_pselect6:
247 case SEN_select:
248 {
249 int i, j;
250 int nfds;
251 kernel_ulong_t *args;
252 kernel_ulong_t select_args[5];
253 unsigned int oldselect_args[5];
254 unsigned int fdsize;
255 fd_set *fds;
256
257 if (SEN_oldselect == s->sen) {
258 if (sizeof(*select_args) == sizeof(*oldselect_args)) {
259 if (umove(tcp, tcp->u_arg[0], &select_args)) {
260 return 0;
261 }
262 } else {
263 unsigned int n;
264
265 if (umove(tcp, tcp->u_arg[0], &oldselect_args)) {
266 return 0;
267 }
268
269 for (n = 0; n < 5; ++n) {
270 select_args[n] = oldselect_args[n];
271 }
272 }
273 args = select_args;
274 } else {
275 args = tcp->u_arg;
276 }
277
278 /* Kernel truncates arg[0] to int, we do the same. */
279 nfds = (int) args[0];
280 /* Kernel rejects negative nfds, so we don't parse it either. */
281 if (nfds <= 0)
282 return 0;
283 /* Beware of select(2^31-1, NULL, NULL, NULL) and similar... */
284 if (nfds > 1024*1024)
285 nfds = 1024*1024;
286 fdsize = (((nfds + 7) / 8) + current_wordsize-1) & -current_wordsize;
287 fds = xmalloc(fdsize);
288
289 for (i = 1; i <= 3; ++i) {
290 if (args[i] == 0)
291 continue;
292 if (umoven(tcp, args[i], fdsize, fds) < 0) {
293 continue;
294 }
295 for (j = 0;; j++) {
296 j = next_set_bit(fds, j, nfds);
297 if (j < 0)
298 break;
299 if (fdmatch(tcp, j)) {
300 free(fds);
301 return 1;
302 }
303 }
304 }
305 free(fds);
306 return 0;
307 }
308
309 case SEN_poll:
310 case SEN_ppoll:
311 {
312 struct pollfd fds;
313 unsigned nfds;
314 kernel_ulong_t start, cur, end;
315
316 start = tcp->u_arg[0];
317 nfds = tcp->u_arg[1];
318
319 end = start + sizeof(fds) * nfds;
320
321 if (nfds == 0 || end < start)
322 return 0;
323
324 for (cur = start; cur < end; cur += sizeof(fds))
325 if ((umove(tcp, cur, &fds) == 0)
326 && fdmatch(tcp, fds.fd))
327 return 1;
328
329 return 0;
330 }
331
332 case SEN_bpf:
333 case SEN_epoll_create:
334 case SEN_epoll_create1:
335 case SEN_eventfd2:
336 case SEN_eventfd:
337 case SEN_fanotify_init:
338 case SEN_inotify_init1:
339 case SEN_memfd_create:
340 case SEN_perf_event_open:
341 case SEN_pipe:
342 case SEN_pipe2:
343 case SEN_printargs:
344 case SEN_socket:
345 case SEN_socketpair:
346 case SEN_timerfd_create:
347 case SEN_timerfd_gettime:
348 case SEN_timerfd_settime:
349 case SEN_userfaultfd:
350 /*
351 * These have TRACE_FILE or TRACE_DESCRIPTOR or TRACE_NETWORK set,
352 * but they don't have any file descriptor or path args to test.
353 */
354 return 0;
355 }
356
357 /*
358 * Our fallback position for calls that haven't already
359 * been handled is to just check arg[0].
360 */
361
362 if (s->sys_flags & TRACE_FILE)
363 return upathmatch(tcp, tcp->u_arg[0]);
364
365 if (s->sys_flags & (TRACE_DESC | TRACE_NETWORK))
366 return fdmatch(tcp, tcp->u_arg[0]);
367
368 return 0;
369 }
370