xref: /linux/drivers/connector/cn_proc.c (revision 68f715a820b02f965e2afc584a6cb542843cbc98) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * cn_proc.c - process events connector
4  *
5  * Copyright (C) Matt Helsley, IBM Corp. 2005
6  * Based on cn_fork.c by Guillaume Thouvenin <guillaume.thouvenin@bull.net>
7  * Original copyright notice follows:
8  * Copyright (C) 2005 BULL SA.
9  */
10 
11 #include <linux/kernel.h>
12 #include <linux/ktime.h>
13 #include <linux/init.h>
14 #include <linux/connector.h>
15 #include <linux/gfp.h>
16 #include <linux/ptrace.h>
17 #include <linux/atomic.h>
18 #include <linux/pid_namespace.h>
19 
20 #include <linux/cn_proc.h>
21 #include <linux/local_lock.h>
22 
23 /*
24  * Size of a cn_msg followed by a proc_event structure.  Since the
25  * sizeof struct cn_msg is a multiple of 4 bytes, but not 8 bytes, we
26  * add one 4-byte word to the size here, and then start the actual
27  * cn_msg structure 4 bytes into the stack buffer.  The result is that
28  * the immediately following proc_event structure is aligned to 8 bytes.
29  */
30 #define CN_PROC_MSG_SIZE (sizeof(struct cn_msg) + sizeof(struct proc_event) + 4)
31 
32 /* See comment above; we test our assumption about sizeof struct cn_msg here. */
33 static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer)
34 {
35 	BUILD_BUG_ON(sizeof(struct cn_msg) != 20);
36 	return (struct cn_msg *)(buffer + 4);
37 }
38 
39 static atomic_t proc_event_num_listeners = ATOMIC_INIT(0);
40 static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC };
41 
42 /* local_event.count is used as the sequence number of the netlink message */
43 struct local_event {
44 	local_lock_t lock;
45 	__u32 count;
46 };
47 static DEFINE_PER_CPU(struct local_event, local_event) = {
48 	.lock = INIT_LOCAL_LOCK(lock),
49 };
50 
51 static int cn_filter(struct sock *dsk, struct sk_buff *skb, void *data)
52 {
53 	__u32 what, exit_code, *ptr;
54 	enum proc_cn_mcast_op mc_op;
55 	uintptr_t val;
56 
57 	if (!dsk || !dsk->sk_user_data || !data)
58 		return 0;
59 
60 	ptr = (__u32 *)data;
61 	what = *ptr++;
62 	exit_code = *ptr;
63 	val = ((struct proc_input *)(dsk->sk_user_data))->event_type;
64 	mc_op = ((struct proc_input *)(dsk->sk_user_data))->mcast_op;
65 
66 	if (mc_op == PROC_CN_MCAST_IGNORE)
67 		return 1;
68 
69 	if ((__u32)val == PROC_EVENT_ALL)
70 		return 0;
71 
72 	/*
73 	 * Drop packet if we have to report only non-zero exit status
74 	 * (PROC_EVENT_NONZERO_EXIT) and exit status is 0
75 	 */
76 	if (((__u32)val & PROC_EVENT_NONZERO_EXIT) &&
77 	    (what == PROC_EVENT_EXIT)) {
78 		if (exit_code)
79 			return 0;
80 	}
81 
82 	if ((__u32)val & what)
83 		return 0;
84 
85 	return 1;
86 }
87 
88 static inline void send_msg(struct cn_msg *msg)
89 {
90 	__u32 filter_data[2];
91 
92 	local_lock(&local_event.lock);
93 
94 	msg->seq = __this_cpu_inc_return(local_event.count) - 1;
95 	((struct proc_event *)msg->data)->cpu = smp_processor_id();
96 
97 	/*
98 	 * local_lock() disables preemption during send to ensure the messages
99 	 * are ordered according to their sequence numbers.
100 	 *
101 	 * If cn_netlink_send() fails, the data is not sent.
102 	 */
103 	filter_data[0] = ((struct proc_event *)msg->data)->what;
104 	if (filter_data[0] == PROC_EVENT_EXIT) {
105 		filter_data[1] =
106 		((struct proc_event *)msg->data)->event_data.exit.exit_code;
107 	} else {
108 		filter_data[1] = 0;
109 	}
110 
111 	if (cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
112 			     cn_filter, (void *)filter_data) == -ESRCH)
113 		atomic_set(&proc_event_num_listeners, 0);
114 
115 	local_unlock(&local_event.lock);
116 }
117 
118 void proc_fork_connector(struct task_struct *task)
119 {
120 	struct cn_msg *msg;
121 	struct proc_event *ev;
122 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
123 	struct task_struct *parent;
124 
125 	if (atomic_read(&proc_event_num_listeners) < 1)
126 		return;
127 
128 	msg = buffer_to_cn_msg(buffer);
129 	ev = (struct proc_event *)msg->data;
130 	memset(&ev->event_data, 0, sizeof(ev->event_data));
131 	ev->timestamp_ns = ktime_get_ns();
132 	ev->what = PROC_EVENT_FORK;
133 	rcu_read_lock();
134 	parent = rcu_dereference(task->real_parent);
135 	ev->event_data.fork.parent_pid = parent->pid;
136 	ev->event_data.fork.parent_tgid = parent->tgid;
137 	rcu_read_unlock();
138 	ev->event_data.fork.child_pid = task->pid;
139 	ev->event_data.fork.child_tgid = task->tgid;
140 
141 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
142 	msg->ack = 0; /* not used */
143 	msg->len = sizeof(*ev);
144 	msg->flags = 0; /* not used */
145 	send_msg(msg);
146 }
147 
148 void proc_exec_connector(struct task_struct *task)
149 {
150 	struct cn_msg *msg;
151 	struct proc_event *ev;
152 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
153 
154 	if (atomic_read(&proc_event_num_listeners) < 1)
155 		return;
156 
157 	msg = buffer_to_cn_msg(buffer);
158 	ev = (struct proc_event *)msg->data;
159 	memset(&ev->event_data, 0, sizeof(ev->event_data));
160 	ev->timestamp_ns = ktime_get_ns();
161 	ev->what = PROC_EVENT_EXEC;
162 	ev->event_data.exec.process_pid = task->pid;
163 	ev->event_data.exec.process_tgid = task->tgid;
164 
165 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
166 	msg->ack = 0; /* not used */
167 	msg->len = sizeof(*ev);
168 	msg->flags = 0; /* not used */
169 	send_msg(msg);
170 }
171 
172 void proc_id_connector(struct task_struct *task, int which_id)
173 {
174 	struct cn_msg *msg;
175 	struct proc_event *ev;
176 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
177 	const struct cred *cred;
178 
179 	if (atomic_read(&proc_event_num_listeners) < 1)
180 		return;
181 
182 	msg = buffer_to_cn_msg(buffer);
183 	ev = (struct proc_event *)msg->data;
184 	memset(&ev->event_data, 0, sizeof(ev->event_data));
185 	ev->what = which_id;
186 	ev->event_data.id.process_pid = task->pid;
187 	ev->event_data.id.process_tgid = task->tgid;
188 	rcu_read_lock();
189 	cred = __task_cred(task);
190 	if (which_id == PROC_EVENT_UID) {
191 		ev->event_data.id.r.ruid = from_kuid_munged(&init_user_ns, cred->uid);
192 		ev->event_data.id.e.euid = from_kuid_munged(&init_user_ns, cred->euid);
193 	} else if (which_id == PROC_EVENT_GID) {
194 		ev->event_data.id.r.rgid = from_kgid_munged(&init_user_ns, cred->gid);
195 		ev->event_data.id.e.egid = from_kgid_munged(&init_user_ns, cred->egid);
196 	} else {
197 		rcu_read_unlock();
198 		return;
199 	}
200 	rcu_read_unlock();
201 	ev->timestamp_ns = ktime_get_ns();
202 
203 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
204 	msg->ack = 0; /* not used */
205 	msg->len = sizeof(*ev);
206 	msg->flags = 0; /* not used */
207 	send_msg(msg);
208 }
209 
210 void proc_sid_connector(struct task_struct *task)
211 {
212 	struct cn_msg *msg;
213 	struct proc_event *ev;
214 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
215 
216 	if (atomic_read(&proc_event_num_listeners) < 1)
217 		return;
218 
219 	msg = buffer_to_cn_msg(buffer);
220 	ev = (struct proc_event *)msg->data;
221 	memset(&ev->event_data, 0, sizeof(ev->event_data));
222 	ev->timestamp_ns = ktime_get_ns();
223 	ev->what = PROC_EVENT_SID;
224 	ev->event_data.sid.process_pid = task->pid;
225 	ev->event_data.sid.process_tgid = task->tgid;
226 
227 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
228 	msg->ack = 0; /* not used */
229 	msg->len = sizeof(*ev);
230 	msg->flags = 0; /* not used */
231 	send_msg(msg);
232 }
233 
234 void proc_ptrace_connector(struct task_struct *task, int ptrace_id)
235 {
236 	struct cn_msg *msg;
237 	struct proc_event *ev;
238 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
239 
240 	if (atomic_read(&proc_event_num_listeners) < 1)
241 		return;
242 
243 	msg = buffer_to_cn_msg(buffer);
244 	ev = (struct proc_event *)msg->data;
245 	memset(&ev->event_data, 0, sizeof(ev->event_data));
246 	ev->timestamp_ns = ktime_get_ns();
247 	ev->what = PROC_EVENT_PTRACE;
248 	ev->event_data.ptrace.process_pid  = task->pid;
249 	ev->event_data.ptrace.process_tgid = task->tgid;
250 	if (ptrace_id == PTRACE_ATTACH) {
251 		ev->event_data.ptrace.tracer_pid  = current->pid;
252 		ev->event_data.ptrace.tracer_tgid = current->tgid;
253 	} else if (ptrace_id == PTRACE_DETACH) {
254 		ev->event_data.ptrace.tracer_pid  = 0;
255 		ev->event_data.ptrace.tracer_tgid = 0;
256 	} else
257 		return;
258 
259 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
260 	msg->ack = 0; /* not used */
261 	msg->len = sizeof(*ev);
262 	msg->flags = 0; /* not used */
263 	send_msg(msg);
264 }
265 
266 void proc_comm_connector(struct task_struct *task)
267 {
268 	struct cn_msg *msg;
269 	struct proc_event *ev;
270 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
271 
272 	if (atomic_read(&proc_event_num_listeners) < 1)
273 		return;
274 
275 	msg = buffer_to_cn_msg(buffer);
276 	ev = (struct proc_event *)msg->data;
277 	memset(&ev->event_data, 0, sizeof(ev->event_data));
278 	ev->timestamp_ns = ktime_get_ns();
279 	ev->what = PROC_EVENT_COMM;
280 	ev->event_data.comm.process_pid  = task->pid;
281 	ev->event_data.comm.process_tgid = task->tgid;
282 	get_task_comm(ev->event_data.comm.comm, task);
283 
284 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
285 	msg->ack = 0; /* not used */
286 	msg->len = sizeof(*ev);
287 	msg->flags = 0; /* not used */
288 	send_msg(msg);
289 }
290 
291 void proc_coredump_connector(struct task_struct *task)
292 {
293 	struct cn_msg *msg;
294 	struct proc_event *ev;
295 	struct task_struct *parent;
296 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
297 
298 	if (atomic_read(&proc_event_num_listeners) < 1)
299 		return;
300 
301 	msg = buffer_to_cn_msg(buffer);
302 	ev = (struct proc_event *)msg->data;
303 	memset(&ev->event_data, 0, sizeof(ev->event_data));
304 	ev->timestamp_ns = ktime_get_ns();
305 	ev->what = PROC_EVENT_COREDUMP;
306 	ev->event_data.coredump.process_pid = task->pid;
307 	ev->event_data.coredump.process_tgid = task->tgid;
308 
309 	rcu_read_lock();
310 	if (pid_alive(task)) {
311 		parent = rcu_dereference(task->real_parent);
312 		ev->event_data.coredump.parent_pid = parent->pid;
313 		ev->event_data.coredump.parent_tgid = parent->tgid;
314 	}
315 	rcu_read_unlock();
316 
317 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
318 	msg->ack = 0; /* not used */
319 	msg->len = sizeof(*ev);
320 	msg->flags = 0; /* not used */
321 	send_msg(msg);
322 }
323 
324 void proc_exit_connector(struct task_struct *task)
325 {
326 	struct cn_msg *msg;
327 	struct proc_event *ev;
328 	struct task_struct *parent;
329 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
330 
331 	if (atomic_read(&proc_event_num_listeners) < 1)
332 		return;
333 
334 	msg = buffer_to_cn_msg(buffer);
335 	ev = (struct proc_event *)msg->data;
336 	memset(&ev->event_data, 0, sizeof(ev->event_data));
337 	ev->timestamp_ns = ktime_get_ns();
338 	ev->what = PROC_EVENT_EXIT;
339 	ev->event_data.exit.process_pid = task->pid;
340 	ev->event_data.exit.process_tgid = task->tgid;
341 	ev->event_data.exit.exit_code = task->exit_code;
342 	ev->event_data.exit.exit_signal = task->exit_signal;
343 
344 	rcu_read_lock();
345 	if (pid_alive(task)) {
346 		parent = rcu_dereference(task->real_parent);
347 		ev->event_data.exit.parent_pid = parent->pid;
348 		ev->event_data.exit.parent_tgid = parent->tgid;
349 	}
350 	rcu_read_unlock();
351 
352 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
353 	msg->ack = 0; /* not used */
354 	msg->len = sizeof(*ev);
355 	msg->flags = 0; /* not used */
356 	send_msg(msg);
357 }
358 
359 /*
360  * Send an acknowledgement message to userspace
361  *
362  * Use 0 for success, EFOO otherwise.
363  * Note: this is the negative of conventional kernel error
364  * values because it's not being returned via syscall return
365  * mechanisms.
366  */
367 static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack)
368 {
369 	struct cn_msg *msg;
370 	struct proc_event *ev;
371 	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
372 
373 	if (atomic_read(&proc_event_num_listeners) < 1)
374 		return;
375 
376 	msg = buffer_to_cn_msg(buffer);
377 	ev = (struct proc_event *)msg->data;
378 	memset(&ev->event_data, 0, sizeof(ev->event_data));
379 	msg->seq = rcvd_seq;
380 	ev->timestamp_ns = ktime_get_ns();
381 	ev->cpu = -1;
382 	ev->what = PROC_EVENT_NONE;
383 	ev->event_data.ack.err = err;
384 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
385 	msg->ack = rcvd_ack + 1;
386 	msg->len = sizeof(*ev);
387 	msg->flags = 0; /* not used */
388 	send_msg(msg);
389 }
390 
391 /**
392  * cn_proc_mcast_ctl
393  * @msg: message sent from userspace via the connector
394  * @nsp: NETLINK_CB of the client's socket buffer
395  */
396 static void cn_proc_mcast_ctl(struct cn_msg *msg,
397 			      struct netlink_skb_parms *nsp)
398 {
399 	enum proc_cn_mcast_op mc_op = 0, prev_mc_op = 0;
400 	struct proc_input *pinput = NULL;
401 	enum proc_cn_event ev_type = 0;
402 	int err = 0, initial = 0;
403 	struct sock *sk = NULL;
404 
405 	/*
406 	 * Events are reported with respect to the initial pid
407 	 * and user namespaces so ignore requestors from
408 	 * other namespaces.
409 	 */
410 	if ((current_user_ns() != &init_user_ns) ||
411 	    !task_is_in_init_pid_ns(current))
412 		return;
413 
414 	if (msg->len == sizeof(*pinput)) {
415 		pinput = (struct proc_input *)msg->data;
416 		mc_op = pinput->mcast_op;
417 		ev_type = pinput->event_type;
418 	} else if (msg->len == sizeof(mc_op)) {
419 		mc_op = *((enum proc_cn_mcast_op *)msg->data);
420 		ev_type = PROC_EVENT_ALL;
421 	} else {
422 		return;
423 	}
424 
425 	ev_type = valid_event((enum proc_cn_event)ev_type);
426 
427 	if (ev_type == PROC_EVENT_NONE)
428 		ev_type = PROC_EVENT_ALL;
429 
430 	if (nsp->sk) {
431 		sk = nsp->sk;
432 		if (sk->sk_user_data == NULL) {
433 			sk->sk_user_data = kzalloc(sizeof(struct proc_input),
434 						   GFP_KERNEL);
435 			if (sk->sk_user_data == NULL) {
436 				err = ENOMEM;
437 				goto out;
438 			}
439 			initial = 1;
440 		} else {
441 			prev_mc_op =
442 			((struct proc_input *)(sk->sk_user_data))->mcast_op;
443 		}
444 		((struct proc_input *)(sk->sk_user_data))->event_type =
445 			ev_type;
446 		((struct proc_input *)(sk->sk_user_data))->mcast_op = mc_op;
447 	}
448 
449 	switch (mc_op) {
450 	case PROC_CN_MCAST_LISTEN:
451 		if (initial || (prev_mc_op != PROC_CN_MCAST_LISTEN))
452 			atomic_inc(&proc_event_num_listeners);
453 		break;
454 	case PROC_CN_MCAST_IGNORE:
455 		if (!initial && (prev_mc_op != PROC_CN_MCAST_IGNORE))
456 			atomic_dec(&proc_event_num_listeners);
457 		((struct proc_input *)(sk->sk_user_data))->event_type =
458 			PROC_EVENT_NONE;
459 		break;
460 	default:
461 		err = EINVAL;
462 		break;
463 	}
464 
465 out:
466 	cn_proc_ack(err, msg->seq, msg->ack);
467 }
468 
469 /*
470  * cn_proc_init - initialization entry point
471  *
472  * Adds the connector callback to the connector driver.
473  */
474 static int __init cn_proc_init(void)
475 {
476 	int err = cn_add_callback(&cn_proc_event_id,
477 				  "cn_proc",
478 				  &cn_proc_mcast_ctl);
479 	if (err) {
480 		pr_warn("cn_proc failed to register\n");
481 		return err;
482 	}
483 	return 0;
484 }
485 device_initcall(cn_proc_init);
486