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1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ | |
2 | ||
3 | #include "errno-util.h" | |
4 | #include "fd-util.h" | |
5 | #include "missing_syscall.h" | |
6 | #include "parse-util.h" | |
7 | #include "pidref.h" | |
8 | #include "process-util.h" | |
9 | #include "signal-util.h" | |
10 | ||
11 | int pidref_set_pid(PidRef *pidref, pid_t pid) { | |
12 | int fd; | |
13 | ||
14 | assert(pidref); | |
15 | ||
16 | if (pid < 0) | |
17 | return -ESRCH; | |
18 | if (pid == 0) | |
19 | pid = getpid_cached(); | |
20 | ||
21 | fd = pidfd_open(pid, 0); | |
22 | if (fd < 0) { | |
23 | /* Graceful fallback in case the kernel doesn't support pidfds or is out of fds */ | |
24 | if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno) && !ERRNO_IS_RESOURCE(errno)) | |
25 | return -errno; | |
26 | ||
27 | fd = -EBADF; | |
28 | } | |
29 | ||
30 | *pidref = (PidRef) { | |
31 | .fd = fd, | |
32 | .pid = pid, | |
33 | }; | |
34 | ||
35 | return 0; | |
36 | } | |
37 | ||
38 | int pidref_set_pidstr(PidRef *pidref, const char *pid) { | |
39 | pid_t nr; | |
40 | int r; | |
41 | ||
42 | assert(pidref); | |
43 | ||
44 | r = parse_pid(pid, &nr); | |
45 | if (r < 0) | |
46 | return r; | |
47 | ||
48 | return pidref_set_pid(pidref, nr); | |
49 | } | |
50 | ||
51 | int pidref_set_pidfd(PidRef *pidref, int fd) { | |
52 | int r; | |
53 | ||
54 | assert(pidref); | |
55 | ||
56 | if (fd < 0) | |
57 | return -EBADF; | |
58 | ||
59 | int fd_copy = fcntl(fd, F_DUPFD_CLOEXEC, 3); | |
60 | if (fd_copy < 0) { | |
61 | pid_t pid; | |
62 | ||
63 | if (!ERRNO_IS_RESOURCE(errno)) | |
64 | return -errno; | |
65 | ||
66 | /* Graceful fallback if we are out of fds */ | |
67 | r = pidfd_get_pid(fd, &pid); | |
68 | if (r < 0) | |
69 | return r; | |
70 | ||
71 | *pidref = PIDREF_MAKE_FROM_PID(pid); | |
72 | return 0; | |
73 | } | |
74 | ||
75 | return pidref_set_pidfd_consume(pidref, fd_copy); | |
76 | } | |
77 | ||
78 | int pidref_set_pidfd_take(PidRef *pidref, int fd) { | |
79 | pid_t pid; | |
80 | int r; | |
81 | ||
82 | assert(pidref); | |
83 | ||
84 | if (fd < 0) | |
85 | return -EBADF; | |
86 | ||
87 | r = pidfd_get_pid(fd, &pid); | |
88 | if (r < 0) | |
89 | return r; | |
90 | ||
91 | *pidref = (PidRef) { | |
92 | .fd = fd, | |
93 | .pid = pid, | |
94 | }; | |
95 | ||
96 | return 0; | |
97 | } | |
98 | ||
99 | int pidref_set_pidfd_consume(PidRef *pidref, int fd) { | |
100 | int r; | |
101 | ||
102 | r = pidref_set_pidfd_take(pidref, fd); | |
103 | if (r < 0) | |
104 | safe_close(fd); | |
105 | ||
106 | return r; | |
107 | } | |
108 | ||
109 | int pidref_set_parent(PidRef *ret) { | |
110 | _cleanup_(pidref_done) PidRef parent = PIDREF_NULL; | |
111 | pid_t ppid; | |
112 | int r; | |
113 | ||
114 | assert(ret); | |
115 | ||
116 | /* Acquires a pidref to our parent process. Deals with the fact that parent processes might exit, and | |
117 | * we get reparented to other processes, with our old parent's PID already being recycled. */ | |
118 | ||
119 | ppid = getppid(); | |
120 | for (;;) { | |
121 | r = pidref_set_pid(&parent, ppid); | |
122 | if (r < 0) | |
123 | return r; | |
124 | ||
125 | if (parent.fd < 0) /* If pidfds are not available, then we are done */ | |
126 | break; | |
127 | ||
128 | pid_t now_ppid = getppid(); | |
129 | if (now_ppid == ppid) /* If our ppid is still the same, then we are done */ | |
130 | break; | |
131 | ||
132 | /* Otherwise let's try again with the new ppid */ | |
133 | ppid = now_ppid; | |
134 | pidref_done(&parent); | |
135 | } | |
136 | ||
137 | *ret = TAKE_PIDREF(parent); | |
138 | return 0; | |
139 | } | |
140 | ||
141 | void pidref_done(PidRef *pidref) { | |
142 | assert(pidref); | |
143 | ||
144 | *pidref = (PidRef) { | |
145 | .fd = safe_close(pidref->fd), | |
146 | }; | |
147 | } | |
148 | ||
149 | PidRef *pidref_free(PidRef *pidref) { | |
150 | /* Regularly, this is an embedded structure. But sometimes we want it on the heap too */ | |
151 | if (!pidref) | |
152 | return NULL; | |
153 | ||
154 | pidref_done(pidref); | |
155 | return mfree(pidref); | |
156 | } | |
157 | ||
158 | int pidref_dup(const PidRef *pidref, PidRef **ret) { | |
159 | _cleanup_close_ int dup_fd = -EBADF; | |
160 | pid_t dup_pid = 0; | |
161 | ||
162 | assert(ret); | |
163 | ||
164 | /* Allocates a new PidRef on the heap, making it a copy of the specified pidref. This does not try to | |
165 | * acquire a pidfd if we don't have one yet! | |
166 | * | |
167 | * If NULL is passed we'll generate a PidRef that refers to no process. This makes it easy to copy | |
168 | * pidref fields that might or might not reference a process yet. */ | |
169 | ||
170 | if (pidref) { | |
171 | if (pidref->fd >= 0) { | |
172 | dup_fd = fcntl(pidref->fd, F_DUPFD_CLOEXEC, 3); | |
173 | if (dup_fd < 0) { | |
174 | if (!ERRNO_IS_RESOURCE(errno)) | |
175 | return -errno; | |
176 | ||
177 | dup_fd = -EBADF; | |
178 | } | |
179 | } | |
180 | ||
181 | if (pidref->pid > 0) | |
182 | dup_pid = pidref->pid; | |
183 | } | |
184 | ||
185 | PidRef *dup_pidref = new(PidRef, 1); | |
186 | if (!dup_pidref) | |
187 | return -ENOMEM; | |
188 | ||
189 | *dup_pidref = (PidRef) { | |
190 | .fd = TAKE_FD(dup_fd), | |
191 | .pid = dup_pid, | |
192 | }; | |
193 | ||
194 | *ret = TAKE_PTR(dup_pidref); | |
195 | return 0; | |
196 | } | |
197 | ||
198 | int pidref_new_from_pid(pid_t pid, PidRef **ret) { | |
199 | _cleanup_(pidref_freep) PidRef *n = 0; | |
200 | int r; | |
201 | ||
202 | assert(ret); | |
203 | ||
204 | if (pid < 0) | |
205 | return -ESRCH; | |
206 | ||
207 | n = new(PidRef, 1); | |
208 | if (!n) | |
209 | return -ENOMEM; | |
210 | ||
211 | *n = PIDREF_NULL; | |
212 | ||
213 | r = pidref_set_pid(n, pid); | |
214 | if (r < 0) | |
215 | return r; | |
216 | ||
217 | *ret = TAKE_PTR(n); | |
218 | return 0; | |
219 | } | |
220 | ||
221 | int pidref_kill(const PidRef *pidref, int sig) { | |
222 | ||
223 | if (!pidref) | |
224 | return -ESRCH; | |
225 | ||
226 | if (pidref->fd >= 0) | |
227 | return RET_NERRNO(pidfd_send_signal(pidref->fd, sig, NULL, 0)); | |
228 | ||
229 | if (pidref->pid > 0) | |
230 | return RET_NERRNO(kill(pidref->pid, sig)); | |
231 | ||
232 | return -ESRCH; | |
233 | } | |
234 | ||
235 | int pidref_kill_and_sigcont(const PidRef *pidref, int sig) { | |
236 | int r; | |
237 | ||
238 | r = pidref_kill(pidref, sig); | |
239 | if (r < 0) | |
240 | return r; | |
241 | ||
242 | if (!IN_SET(sig, SIGCONT, SIGKILL)) | |
243 | (void) pidref_kill(pidref, SIGCONT); | |
244 | ||
245 | return 0; | |
246 | } | |
247 | ||
248 | int pidref_sigqueue(const PidRef *pidref, int sig, int value) { | |
249 | ||
250 | if (!pidref) | |
251 | return -ESRCH; | |
252 | ||
253 | if (pidref->fd >= 0) { | |
254 | siginfo_t si; | |
255 | ||
256 | /* We can't use structured initialization here, since the structure contains various unions | |
257 | * and these fields lie in overlapping (carefully aligned) unions that LLVM is allergic to | |
258 | * allow assignments to */ | |
259 | zero(si); | |
260 | si.si_signo = sig; | |
261 | si.si_code = SI_QUEUE; | |
262 | si.si_pid = getpid_cached(); | |
263 | si.si_uid = getuid(); | |
264 | si.si_value.sival_int = value; | |
265 | ||
266 | return RET_NERRNO(pidfd_send_signal(pidref->fd, sig, &si, 0)); | |
267 | } | |
268 | ||
269 | if (pidref->pid > 0) | |
270 | return RET_NERRNO(sigqueue(pidref->pid, sig, (const union sigval) { .sival_int = value })); | |
271 | ||
272 | return -ESRCH; | |
273 | } | |
274 | ||
275 | int pidref_verify(const PidRef *pidref) { | |
276 | int r; | |
277 | ||
278 | /* This is a helper that is supposed to be called after reading information from procfs via a | |
279 | * PidRef. It ensures that the PID we track still matches the PIDFD we pin. If this value differs | |
280 | * after a procfs read, we might have read the data from a recycled PID. */ | |
281 | ||
282 | if (!pidref_is_set(pidref)) | |
283 | return -ESRCH; | |
284 | ||
285 | if (pidref->pid == 1) | |
286 | return 1; /* PID 1 can never go away, hence never be recycled to a different process → return 1 */ | |
287 | ||
288 | if (pidref->fd < 0) | |
289 | return 0; /* If we don't have a pidfd we cannot validate it, hence we assume it's all OK → return 0 */ | |
290 | ||
291 | r = pidfd_verify_pid(pidref->fd, pidref->pid); | |
292 | if (r < 0) | |
293 | return r; | |
294 | ||
295 | return 1; /* We have a pidfd and it still points to the PID we have, hence all is *really* OK → return 1 */ | |
296 | } | |
297 | ||
298 | bool pidref_is_self(const PidRef *pidref) { | |
299 | if (!pidref) | |
300 | return false; | |
301 | ||
302 | return pidref->pid == getpid_cached(); | |
303 | } | |
304 | ||
305 | static void pidref_hash_func(const PidRef *pidref, struct siphash *state) { | |
306 | siphash24_compress(&pidref->pid, sizeof(pidref->pid), state); | |
307 | } | |
308 | ||
309 | static int pidref_compare_func(const PidRef *a, const PidRef *b) { | |
310 | return CMP(a->pid, b->pid); | |
311 | } | |
312 | ||
313 | DEFINE_HASH_OPS(pidref_hash_ops, PidRef, pidref_hash_func, pidref_compare_func); | |
314 | ||
315 | DEFINE_HASH_OPS_WITH_KEY_DESTRUCTOR(pidref_hash_ops_free, | |
316 | PidRef, pidref_hash_func, pidref_compare_func, | |
317 | pidref_free); |