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