1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Support for async notification of waitid
4 */
5#include <linux/kernel.h>
6#include <linux/errno.h>
7#include <linux/fs.h>
8#include <linux/file.h>
9#include <linux/compat.h>
10#include <linux/io_uring.h>
11
12#include <uapi/linux/io_uring.h>
13
14#include "io_uring.h"
15#include "cancel.h"
16#include "waitid.h"
17#include "../kernel/exit.h"
18
19static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts);
20
21#define IO_WAITID_CANCEL_FLAG BIT(31)
22#define IO_WAITID_REF_MASK GENMASK(30, 0)
23
24struct io_waitid {
25 struct file *file;
26 int which;
27 pid_t upid;
28 int options;
29 atomic_t refs;
30 struct wait_queue_head *head;
31 struct siginfo __user *infop;
32 struct waitid_info info;
33};
34
35static void io_waitid_free(struct io_kiocb *req)
36{
37 struct io_waitid_async *iwa = req->async_data;
38
39 put_pid(pid: iwa->wo.wo_pid);
40 kfree(objp: req->async_data);
41 req->async_data = NULL;
42 req->flags &= ~REQ_F_ASYNC_DATA;
43}
44
45#ifdef CONFIG_COMPAT
46static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo)
47{
48 struct compat_siginfo __user *infop;
49 bool ret;
50
51 infop = (struct compat_siginfo __user *) iw->infop;
52
53 if (!user_write_access_begin(infop, sizeof(*infop)))
54 return false;
55
56 unsafe_put_user(signo, &infop->si_signo, Efault);
57 unsafe_put_user(0, &infop->si_errno, Efault);
58 unsafe_put_user(iw->info.cause, &infop->si_code, Efault);
59 unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);
60 unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);
61 unsafe_put_user(iw->info.status, &infop->si_status, Efault);
62 ret = true;
63done:
64 user_write_access_end();
65 return ret;
66Efault:
67 ret = false;
68 goto done;
69}
70#endif
71
72static bool io_waitid_copy_si(struct io_kiocb *req, int signo)
73{
74 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
75 bool ret;
76
77 if (!iw->infop)
78 return true;
79
80#ifdef CONFIG_COMPAT
81 if (req->ctx->compat)
82 return io_waitid_compat_copy_si(iw, signo);
83#endif
84
85 if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))
86 return false;
87
88 unsafe_put_user(signo, &iw->infop->si_signo, Efault);
89 unsafe_put_user(0, &iw->infop->si_errno, Efault);
90 unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);
91 unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);
92 unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);
93 unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);
94 ret = true;
95done:
96 user_write_access_end();
97 return ret;
98Efault:
99 ret = false;
100 goto done;
101}
102
103static int io_waitid_finish(struct io_kiocb *req, int ret)
104{
105 int signo = 0;
106
107 if (ret > 0) {
108 signo = SIGCHLD;
109 ret = 0;
110 }
111
112 if (!io_waitid_copy_si(req, signo))
113 ret = -EFAULT;
114 io_waitid_free(req);
115 return ret;
116}
117
118static void io_waitid_complete(struct io_kiocb *req, int ret)
119{
120 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
121 struct io_tw_state ts = { .locked = true };
122
123 /* anyone completing better be holding a reference */
124 WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK));
125
126 lockdep_assert_held(&req->ctx->uring_lock);
127
128 hlist_del_init(n: &req->hash_node);
129
130 ret = io_waitid_finish(req, ret);
131 if (ret < 0)
132 req_set_fail(req);
133 io_req_set_res(req, res: ret, cflags: 0);
134 io_req_task_complete(req, ts: &ts);
135}
136
137static bool __io_waitid_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)
138{
139 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
140 struct io_waitid_async *iwa = req->async_data;
141
142 /*
143 * Mark us canceled regardless of ownership. This will prevent a
144 * potential retry from a spurious wakeup.
145 */
146 atomic_or(IO_WAITID_CANCEL_FLAG, v: &iw->refs);
147
148 /* claim ownership */
149 if (atomic_fetch_inc(v: &iw->refs) & IO_WAITID_REF_MASK)
150 return false;
151
152 spin_lock_irq(lock: &iw->head->lock);
153 list_del_init(entry: &iwa->wo.child_wait.entry);
154 spin_unlock_irq(lock: &iw->head->lock);
155 io_waitid_complete(req, ret: -ECANCELED);
156 return true;
157}
158
159int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
160 unsigned int issue_flags)
161{
162 struct hlist_node *tmp;
163 struct io_kiocb *req;
164 int nr = 0;
165
166 if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_FD_FIXED))
167 return -ENOENT;
168
169 io_ring_submit_lock(ctx, issue_flags);
170 hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
171 if (req->cqe.user_data != cd->data &&
172 !(cd->flags & IORING_ASYNC_CANCEL_ANY))
173 continue;
174 if (__io_waitid_cancel(ctx, req))
175 nr++;
176 if (!(cd->flags & IORING_ASYNC_CANCEL_ALL))
177 break;
178 }
179 io_ring_submit_unlock(ctx, issue_flags);
180
181 if (nr)
182 return nr;
183
184 return -ENOENT;
185}
186
187bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
188 bool cancel_all)
189{
190 struct hlist_node *tmp;
191 struct io_kiocb *req;
192 bool found = false;
193
194 lockdep_assert_held(&ctx->uring_lock);
195
196 hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
197 if (!io_match_task_safe(head: req, task, cancel_all))
198 continue;
199 hlist_del_init(n: &req->hash_node);
200 __io_waitid_cancel(ctx, req);
201 found = true;
202 }
203
204 return found;
205}
206
207static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
208{
209 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
210 struct io_waitid_async *iwa = req->async_data;
211
212 if (!atomic_sub_return(i: 1, v: &iw->refs))
213 return false;
214
215 /*
216 * Wakeup triggered, racing with us. It was prevented from
217 * completing because of that, queue up the tw to do that.
218 */
219 req->io_task_work.func = io_waitid_cb;
220 io_req_task_work_add(req);
221 remove_wait_queue(wq_head: iw->head, wq_entry: &iwa->wo.child_wait);
222 return true;
223}
224
225static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts)
226{
227 struct io_waitid_async *iwa = req->async_data;
228 struct io_ring_ctx *ctx = req->ctx;
229 int ret;
230
231 io_tw_lock(ctx, ts);
232
233 ret = __do_wait(wo: &iwa->wo);
234
235 /*
236 * If we get -ERESTARTSYS here, we need to re-arm and check again
237 * to ensure we get another callback. If the retry works, then we can
238 * just remove ourselves from the waitqueue again and finish the
239 * request.
240 */
241 if (unlikely(ret == -ERESTARTSYS)) {
242 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
243
244 /* Don't retry if cancel found it meanwhile */
245 ret = -ECANCELED;
246 if (!(atomic_read(v: &iw->refs) & IO_WAITID_CANCEL_FLAG)) {
247 iw->head = &current->signal->wait_chldexit;
248 add_wait_queue(wq_head: iw->head, wq_entry: &iwa->wo.child_wait);
249 ret = __do_wait(wo: &iwa->wo);
250 if (ret == -ERESTARTSYS) {
251 /* retry armed, drop our ref */
252 io_waitid_drop_issue_ref(req);
253 return;
254 }
255
256 remove_wait_queue(wq_head: iw->head, wq_entry: &iwa->wo.child_wait);
257 }
258 }
259
260 io_waitid_complete(req, ret);
261}
262
263static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
264 int sync, void *key)
265{
266 struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);
267 struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);
268 struct io_kiocb *req = iwa->req;
269 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
270 struct task_struct *p = key;
271
272 if (!pid_child_should_wake(wo, p))
273 return 0;
274
275 /* cancel is in progress */
276 if (atomic_fetch_inc(v: &iw->refs) & IO_WAITID_REF_MASK)
277 return 1;
278
279 req->io_task_work.func = io_waitid_cb;
280 io_req_task_work_add(req);
281 list_del_init(entry: &wait->entry);
282 return 1;
283}
284
285int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
286{
287 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
288
289 if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
290 return -EINVAL;
291
292 iw->which = READ_ONCE(sqe->len);
293 iw->upid = READ_ONCE(sqe->fd);
294 iw->options = READ_ONCE(sqe->file_index);
295 iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
296 return 0;
297}
298
299int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
300{
301 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
302 struct io_ring_ctx *ctx = req->ctx;
303 struct io_waitid_async *iwa;
304 int ret;
305
306 if (io_alloc_async_data(req))
307 return -ENOMEM;
308
309 iwa = req->async_data;
310 iwa->req = req;
311
312 ret = kernel_waitid_prepare(wo: &iwa->wo, which: iw->which, upid: iw->upid, infop: &iw->info,
313 options: iw->options, NULL);
314 if (ret)
315 goto done;
316
317 /*
318 * Mark the request as busy upfront, in case we're racing with the
319 * wakeup. If we are, then we'll notice when we drop this initial
320 * reference again after arming.
321 */
322 atomic_set(v: &iw->refs, i: 1);
323
324 /*
325 * Cancel must hold the ctx lock, so there's no risk of cancelation
326 * finding us until a) we remain on the list, and b) the lock is
327 * dropped. We only need to worry about racing with the wakeup
328 * callback.
329 */
330 io_ring_submit_lock(ctx, issue_flags);
331 hlist_add_head(n: &req->hash_node, h: &ctx->waitid_list);
332
333 init_waitqueue_func_entry(wq_entry: &iwa->wo.child_wait, func: io_waitid_wait);
334 iwa->wo.child_wait.private = req->task;
335 iw->head = &current->signal->wait_chldexit;
336 add_wait_queue(wq_head: iw->head, wq_entry: &iwa->wo.child_wait);
337
338 ret = __do_wait(wo: &iwa->wo);
339 if (ret == -ERESTARTSYS) {
340 /*
341 * Nobody else grabbed a reference, it'll complete when we get
342 * a waitqueue callback, or if someone cancels it.
343 */
344 if (!io_waitid_drop_issue_ref(req)) {
345 io_ring_submit_unlock(ctx, issue_flags);
346 return IOU_ISSUE_SKIP_COMPLETE;
347 }
348
349 /*
350 * Wakeup triggered, racing with us. It was prevented from
351 * completing because of that, queue up the tw to do that.
352 */
353 io_ring_submit_unlock(ctx, issue_flags);
354 return IOU_ISSUE_SKIP_COMPLETE;
355 }
356
357 hlist_del_init(n: &req->hash_node);
358 remove_wait_queue(wq_head: iw->head, wq_entry: &iwa->wo.child_wait);
359 ret = io_waitid_finish(req, ret);
360
361 io_ring_submit_unlock(ctx, issue_flags);
362done:
363 if (ret < 0)
364 req_set_fail(req);
365 io_req_set_res(req, res: ret, cflags: 0);
366 return IOU_OK;
367}
368

source code of linux/io_uring/waitid.c