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 19 static 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 24 struct 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 35 static void io_waitid_free(struct io_kiocb *req) 36 { 37 struct io_waitid_async *iwa = req->async_data; 38 39 put_pid(iwa->wo.wo_pid); 40 kfree(req->async_data); 41 req->async_data = NULL; 42 req->flags &= ~REQ_F_ASYNC_DATA; 43 } 44 45 #ifdef CONFIG_COMPAT 46 static 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; 63 done: 64 user_write_access_end(); 65 return ret; 66 Efault: 67 ret = false; 68 goto done; 69 } 70 #endif 71 72 static 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; 95 done: 96 user_write_access_end(); 97 return ret; 98 Efault: 99 ret = false; 100 goto done; 101 } 102 103 static 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 } 117 118 static 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 /* 129 * Did cancel find it meanwhile? 130 */ 131 if (hlist_unhashed(&req->hash_node)) 132 return; 133 134 hlist_del_init(&req->hash_node); 135 136 ret = io_waitid_finish(req, ret); 137 if (ret < 0) 138 req_set_fail(req); 139 io_req_set_res(req, ret, 0); 140 io_req_task_complete(req, &ts); 141 } 142 143 static bool __io_waitid_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req) 144 { 145 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 146 struct io_waitid_async *iwa = req->async_data; 147 148 /* 149 * Mark us canceled regardless of ownership. This will prevent a 150 * potential retry from a spurious wakeup. 151 */ 152 atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs); 153 154 /* claim ownership */ 155 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 156 return false; 157 158 spin_lock_irq(&iw->head->lock); 159 list_del_init(&iwa->wo.child_wait.entry); 160 spin_unlock_irq(&iw->head->lock); 161 io_waitid_complete(req, -ECANCELED); 162 return true; 163 } 164 165 int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, 166 unsigned int issue_flags) 167 { 168 struct hlist_node *tmp; 169 struct io_kiocb *req; 170 int nr = 0; 171 172 if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_FD_FIXED)) 173 return -ENOENT; 174 175 io_ring_submit_lock(ctx, issue_flags); 176 hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) { 177 if (req->cqe.user_data != cd->data && 178 !(cd->flags & IORING_ASYNC_CANCEL_ANY)) 179 continue; 180 if (__io_waitid_cancel(ctx, req)) 181 nr++; 182 if (!(cd->flags & IORING_ASYNC_CANCEL_ALL)) 183 break; 184 } 185 io_ring_submit_unlock(ctx, issue_flags); 186 187 if (nr) 188 return nr; 189 190 return -ENOENT; 191 } 192 193 bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task, 194 bool cancel_all) 195 { 196 struct hlist_node *tmp; 197 struct io_kiocb *req; 198 bool found = false; 199 200 lockdep_assert_held(&ctx->uring_lock); 201 202 hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) { 203 if (!io_match_task_safe(req, task, cancel_all)) 204 continue; 205 __io_waitid_cancel(ctx, req); 206 found = true; 207 } 208 209 return found; 210 } 211 212 static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req) 213 { 214 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 215 struct io_waitid_async *iwa = req->async_data; 216 217 if (!atomic_sub_return(1, &iw->refs)) 218 return false; 219 220 /* 221 * Wakeup triggered, racing with us. It was prevented from 222 * completing because of that, queue up the tw to do that. 223 */ 224 req->io_task_work.func = io_waitid_cb; 225 io_req_task_work_add(req); 226 remove_wait_queue(iw->head, &iwa->wo.child_wait); 227 return true; 228 } 229 230 static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts) 231 { 232 struct io_waitid_async *iwa = req->async_data; 233 struct io_ring_ctx *ctx = req->ctx; 234 int ret; 235 236 io_tw_lock(ctx, ts); 237 238 ret = __do_wait(&iwa->wo); 239 240 /* 241 * If we get -ERESTARTSYS here, we need to re-arm and check again 242 * to ensure we get another callback. If the retry works, then we can 243 * just remove ourselves from the waitqueue again and finish the 244 * request. 245 */ 246 if (unlikely(ret == -ERESTARTSYS)) { 247 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 248 249 /* Don't retry if cancel found it meanwhile */ 250 ret = -ECANCELED; 251 if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) { 252 iw->head = ¤t->signal->wait_chldexit; 253 add_wait_queue(iw->head, &iwa->wo.child_wait); 254 ret = __do_wait(&iwa->wo); 255 if (ret == -ERESTARTSYS) { 256 /* retry armed, drop our ref */ 257 io_waitid_drop_issue_ref(req); 258 return; 259 } 260 261 remove_wait_queue(iw->head, &iwa->wo.child_wait); 262 } 263 } 264 265 io_waitid_complete(req, ret); 266 } 267 268 static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode, 269 int sync, void *key) 270 { 271 struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait); 272 struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo); 273 struct io_kiocb *req = iwa->req; 274 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 275 struct task_struct *p = key; 276 277 if (!pid_child_should_wake(wo, p)) 278 return 0; 279 280 /* cancel is in progress */ 281 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 282 return 1; 283 284 req->io_task_work.func = io_waitid_cb; 285 io_req_task_work_add(req); 286 list_del_init(&wait->entry); 287 return 1; 288 } 289 290 int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 291 { 292 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 293 294 if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags) 295 return -EINVAL; 296 297 iw->which = READ_ONCE(sqe->len); 298 iw->upid = READ_ONCE(sqe->fd); 299 iw->options = READ_ONCE(sqe->file_index); 300 iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2)); 301 return 0; 302 } 303 304 int io_waitid(struct io_kiocb *req, unsigned int issue_flags) 305 { 306 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 307 struct io_ring_ctx *ctx = req->ctx; 308 struct io_waitid_async *iwa; 309 int ret; 310 311 if (io_alloc_async_data(req)) 312 return -ENOMEM; 313 314 iwa = req->async_data; 315 iwa->req = req; 316 317 ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info, 318 iw->options, NULL); 319 if (ret) 320 goto done; 321 322 /* 323 * Mark the request as busy upfront, in case we're racing with the 324 * wakeup. If we are, then we'll notice when we drop this initial 325 * reference again after arming. 326 */ 327 atomic_set(&iw->refs, 1); 328 329 /* 330 * Cancel must hold the ctx lock, so there's no risk of cancelation 331 * finding us until a) we remain on the list, and b) the lock is 332 * dropped. We only need to worry about racing with the wakeup 333 * callback. 334 */ 335 io_ring_submit_lock(ctx, issue_flags); 336 hlist_add_head(&req->hash_node, &ctx->waitid_list); 337 338 init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait); 339 iwa->wo.child_wait.private = req->task; 340 iw->head = ¤t->signal->wait_chldexit; 341 add_wait_queue(iw->head, &iwa->wo.child_wait); 342 343 ret = __do_wait(&iwa->wo); 344 if (ret == -ERESTARTSYS) { 345 /* 346 * Nobody else grabbed a reference, it'll complete when we get 347 * a waitqueue callback, or if someone cancels it. 348 */ 349 if (!io_waitid_drop_issue_ref(req)) { 350 io_ring_submit_unlock(ctx, issue_flags); 351 return IOU_ISSUE_SKIP_COMPLETE; 352 } 353 354 /* 355 * Wakeup triggered, racing with us. It was prevented from 356 * completing because of that, queue up the tw to do that. 357 */ 358 io_ring_submit_unlock(ctx, issue_flags); 359 return IOU_ISSUE_SKIP_COMPLETE; 360 } 361 362 hlist_del_init(&req->hash_node); 363 remove_wait_queue(iw->head, &iwa->wo.child_wait); 364 ret = io_waitid_finish(req, ret); 365 366 io_ring_submit_unlock(ctx, issue_flags); 367 done: 368 if (ret < 0) 369 req_set_fail(req); 370 io_req_set_res(req, ret, 0); 371 return IOU_OK; 372 } 373