1// SPDX-License-Identifier: GPL-2.0-only
  2/* Copyright (c) 2020 Facebook */
  3
  4#include <linux/init.h>
  5#include <linux/namei.h>
  6#include <linux/pid_namespace.h>
  7#include <linux/fs.h>
  8#include <linux/fdtable.h>
  9#include <linux/filter.h>
 10#include <linux/btf_ids.h>
 11
 12struct bpf_iter_seq_task_common {
 13	struct pid_namespace *ns;
 14};
 15
 16struct bpf_iter_seq_task_info {
 17	/* The first field must be struct bpf_iter_seq_task_common.
 18	 * this is assumed by {init, fini}_seq_pidns() callback functions.
 19	 */
 20	struct bpf_iter_seq_task_common common;
 21	u32 tid;
 22};
 23
 24static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
 25					     u32 *tid)
 26{
 27	struct task_struct *task = NULL;
 28	struct pid *pid;
 29
 30	rcu_read_lock();
 31retry:
 32	pid = find_ge_pid(*tid, ns);
 33	if (pid) {
 34		*tid = pid_nr_ns(pid, ns);
 35		task = get_pid_task(pid, PIDTYPE_PID);
 36		if (!task) {
 37			++*tid;
 38			goto retry;
 39		}
 40	}
 41	rcu_read_unlock();
 42
 43	return task;
 44}
 45
 46static void *task_seq_start(struct seq_file *seq, loff_t *pos)
 47{
 48	struct bpf_iter_seq_task_info *info = seq->private;
 49	struct task_struct *task;
 50
 51	task = task_seq_get_next(info->common.ns, &info->tid);
 52	if (!task)
 53		return NULL;
 54
 55	if (*pos == 0)
 56		++*pos;
 57	return task;
 58}
 59
 60static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 61{
 62	struct bpf_iter_seq_task_info *info = seq->private;
 63	struct task_struct *task;
 64
 65	++*pos;
 66	++info->tid;
 67	put_task_struct((struct task_struct *)v);
 68	task = task_seq_get_next(info->common.ns, &info->tid);
 69	if (!task)
 70		return NULL;
 71
 72	return task;
 73}
 74
 75struct bpf_iter__task {
 76	__bpf_md_ptr(struct bpf_iter_meta *, meta);
 77	__bpf_md_ptr(struct task_struct *, task);
 78};
 79
 80DEFINE_BPF_ITER_FUNC(task, struct bpf_iter_meta *meta, struct task_struct *task)
 81
 82static int __task_seq_show(struct seq_file *seq, struct task_struct *task,
 83			   bool in_stop)
 84{
 85	struct bpf_iter_meta meta;
 86	struct bpf_iter__task ctx;
 87	struct bpf_prog *prog;
 88
 89	meta.seq = seq;
 90	prog = bpf_iter_get_info(&meta, in_stop);
 91	if (!prog)
 92		return 0;
 93
 94	meta.seq = seq;
 95	ctx.meta = &meta;
 96	ctx.task = task;
 97	return bpf_iter_run_prog(prog, &ctx);
 98}
 99
100static int task_seq_show(struct seq_file *seq, void *v)
101{
102	return __task_seq_show(seq, v, false);
103}
104
105static void task_seq_stop(struct seq_file *seq, void *v)
106{
107	if (!v)
108		(void)__task_seq_show(seq, v, true);
109	else
110		put_task_struct((struct task_struct *)v);
111}
112
113static const struct seq_operations task_seq_ops = {
114	.start	= task_seq_start,
115	.next	= task_seq_next,
116	.stop	= task_seq_stop,
117	.show	= task_seq_show,
118};
119
120struct bpf_iter_seq_task_file_info {
121	/* The first field must be struct bpf_iter_seq_task_common.
122	 * this is assumed by {init, fini}_seq_pidns() callback functions.
123	 */
124	struct bpf_iter_seq_task_common common;
125	struct task_struct *task;
126	struct files_struct *files;
127	u32 tid;
128	u32 fd;
129};
130
131static struct file *
132task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,
133		       struct task_struct **task, struct files_struct **fstruct)
134{
135	struct pid_namespace *ns = info->common.ns;
136	u32 curr_tid = info->tid, max_fds;
137	struct files_struct *curr_files;
138	struct task_struct *curr_task;
139	int curr_fd = info->fd;
140
141	/* If this function returns a non-NULL file object,
142	 * it held a reference to the task/files_struct/file.
143	 * Otherwise, it does not hold any reference.
144	 */
145again:
146	if (*task) {
147		curr_task = *task;
148		curr_files = *fstruct;
149		curr_fd = info->fd;
150	} else {
151		curr_task = task_seq_get_next(ns, &curr_tid);
152		if (!curr_task)
153			return NULL;
154
155		curr_files = get_files_struct(curr_task);
156		if (!curr_files) {
157			put_task_struct(curr_task);
158			curr_tid = ++(info->tid);
159			info->fd = 0;
160			goto again;
161		}
162
163		/* set *fstruct, *task and info->tid */
164		*fstruct = curr_files;
165		*task = curr_task;
166		if (curr_tid == info->tid) {
167			curr_fd = info->fd;
168		} else {
169			info->tid = curr_tid;
170			curr_fd = 0;
171		}
172	}
173
174	rcu_read_lock();
175	max_fds = files_fdtable(curr_files)->max_fds;
176	for (; curr_fd < max_fds; curr_fd++) {
177		struct file *f;
178
179		f = fcheck_files(curr_files, curr_fd);
180		if (!f)
181			continue;
182		if (!get_file_rcu(f))
183			continue;
184
185		/* set info->fd */
186		info->fd = curr_fd;
187		rcu_read_unlock();
188		return f;
189	}
190
191	/* the current task is done, go to the next task */
192	rcu_read_unlock();
193	put_files_struct(curr_files);
194	put_task_struct(curr_task);
195	*task = NULL;
196	*fstruct = NULL;
197	info->fd = 0;
198	curr_tid = ++(info->tid);
199	goto again;
200}
201
202static void *task_file_seq_start(struct seq_file *seq, loff_t *pos)
203{
204	struct bpf_iter_seq_task_file_info *info = seq->private;
205	struct files_struct *files = NULL;
206	struct task_struct *task = NULL;
207	struct file *file;
208
209	file = task_file_seq_get_next(info, &task, &files);
210	if (!file) {
211		info->files = NULL;
212		info->task = NULL;
213		return NULL;
214	}
215
216	if (*pos == 0)
217		++*pos;
218	info->task = task;
219	info->files = files;
220
221	return file;
222}
223
224static void *task_file_seq_next(struct seq_file *seq, void *v, loff_t *pos)
225{
226	struct bpf_iter_seq_task_file_info *info = seq->private;
227	struct files_struct *files = info->files;
228	struct task_struct *task = info->task;
229	struct file *file;
230
231	++*pos;
232	++info->fd;
233	fput((struct file *)v);
234	file = task_file_seq_get_next(info, &task, &files);
235	if (!file) {
236		info->files = NULL;
237		info->task = NULL;
238		return NULL;
239	}
240
241	info->task = task;
242	info->files = files;
243
244	return file;
245}
246
247struct bpf_iter__task_file {
248	__bpf_md_ptr(struct bpf_iter_meta *, meta);
249	__bpf_md_ptr(struct task_struct *, task);
250	u32 fd __aligned(8);
251	__bpf_md_ptr(struct file *, file);
252};
253
254DEFINE_BPF_ITER_FUNC(task_file, struct bpf_iter_meta *meta,
255		     struct task_struct *task, u32 fd,
256		     struct file *file)
257
258static int __task_file_seq_show(struct seq_file *seq, struct file *file,
259				bool in_stop)
260{
261	struct bpf_iter_seq_task_file_info *info = seq->private;
262	struct bpf_iter__task_file ctx;
263	struct bpf_iter_meta meta;
264	struct bpf_prog *prog;
265
266	meta.seq = seq;
267	prog = bpf_iter_get_info(&meta, in_stop);
268	if (!prog)
269		return 0;
270
271	ctx.meta = &meta;
272	ctx.task = info->task;
273	ctx.fd = info->fd;
274	ctx.file = file;
275	return bpf_iter_run_prog(prog, &ctx);
276}
277
278static int task_file_seq_show(struct seq_file *seq, void *v)
279{
280	return __task_file_seq_show(seq, v, false);
281}
282
283static void task_file_seq_stop(struct seq_file *seq, void *v)
284{
285	struct bpf_iter_seq_task_file_info *info = seq->private;
286
287	if (!v) {
288		(void)__task_file_seq_show(seq, v, true);
289	} else {
290		fput((struct file *)v);
291		put_files_struct(info->files);
292		put_task_struct(info->task);
293		info->files = NULL;
294		info->task = NULL;
295	}
296}
297
298static int init_seq_pidns(void *priv_data, struct bpf_iter_aux_info *aux)
299{
300	struct bpf_iter_seq_task_common *common = priv_data;
301
302	common->ns = get_pid_ns(task_active_pid_ns(current));
303	return 0;
304}
305
306static void fini_seq_pidns(void *priv_data)
307{
308	struct bpf_iter_seq_task_common *common = priv_data;
309
310	put_pid_ns(common->ns);
311}
312
313static const struct seq_operations task_file_seq_ops = {
314	.start	= task_file_seq_start,
315	.next	= task_file_seq_next,
316	.stop	= task_file_seq_stop,
317	.show	= task_file_seq_show,
318};
319
320BTF_ID_LIST(btf_task_file_ids)
321BTF_ID(struct, task_struct)
322BTF_ID(struct, file)
323
324static const struct bpf_iter_seq_info task_seq_info = {
325	.seq_ops		= &task_seq_ops,
326	.init_seq_private	= init_seq_pidns,
327	.fini_seq_private	= fini_seq_pidns,
328	.seq_priv_size		= sizeof(struct bpf_iter_seq_task_info),
329};
330
331static struct bpf_iter_reg task_reg_info = {
332	.target			= "task",
333	.ctx_arg_info_size	= 1,
334	.ctx_arg_info		= {
335		{ offsetof(struct bpf_iter__task, task),
336		  PTR_TO_BTF_ID_OR_NULL },
337	},
338	.seq_info		= &task_seq_info,
339};
340
341static const struct bpf_iter_seq_info task_file_seq_info = {
342	.seq_ops		= &task_file_seq_ops,
343	.init_seq_private	= init_seq_pidns,
344	.fini_seq_private	= fini_seq_pidns,
345	.seq_priv_size		= sizeof(struct bpf_iter_seq_task_file_info),
346};
347
348static struct bpf_iter_reg task_file_reg_info = {
349	.target			= "task_file",
350	.ctx_arg_info_size	= 2,
351	.ctx_arg_info		= {
352		{ offsetof(struct bpf_iter__task_file, task),
353		  PTR_TO_BTF_ID_OR_NULL },
354		{ offsetof(struct bpf_iter__task_file, file),
355		  PTR_TO_BTF_ID_OR_NULL },
356	},
357	.seq_info		= &task_file_seq_info,
358};
359
360static int __init task_iter_init(void)
361{
362	int ret;
363
364	task_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
365	ret = bpf_iter_reg_target(&task_reg_info);
366	if (ret)
367		return ret;
368
369	task_file_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
370	task_file_reg_info.ctx_arg_info[1].btf_id = btf_task_file_ids[1];
371	return bpf_iter_reg_target(&task_file_reg_info);
372}
373late_initcall(task_iter_init);