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_tw_req tw_req, io_tw_token_t tw); 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 io_req_async_data_free(req); 41 } 42 43 static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo) 44 { 45 struct compat_siginfo __user *infop; 46 bool ret; 47 48 infop = (struct compat_siginfo __user *) iw->infop; 49 50 if (!user_write_access_begin(infop, sizeof(*infop))) 51 return false; 52 53 unsafe_put_user(signo, &infop->si_signo, Efault); 54 unsafe_put_user(0, &infop->si_errno, Efault); 55 unsafe_put_user(iw->info.cause, &infop->si_code, Efault); 56 unsafe_put_user(iw->info.pid, &infop->si_pid, Efault); 57 unsafe_put_user(iw->info.uid, &infop->si_uid, Efault); 58 unsafe_put_user(iw->info.status, &infop->si_status, Efault); 59 ret = true; 60 done: 61 user_write_access_end(); 62 return ret; 63 Efault: 64 ret = false; 65 goto done; 66 } 67 68 static bool io_waitid_copy_si(struct io_kiocb *req, int signo) 69 { 70 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 71 bool ret; 72 73 if (!iw->infop) 74 return true; 75 76 if (io_is_compat(req->ctx)) 77 return io_waitid_compat_copy_si(iw, signo); 78 79 if (!user_write_access_begin(iw->infop, sizeof(*iw->infop))) 80 return false; 81 82 unsafe_put_user(signo, &iw->infop->si_signo, Efault); 83 unsafe_put_user(0, &iw->infop->si_errno, Efault); 84 unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault); 85 unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault); 86 unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault); 87 unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault); 88 ret = true; 89 done: 90 user_write_access_end(); 91 return ret; 92 Efault: 93 ret = false; 94 goto done; 95 } 96 97 static int io_waitid_finish(struct io_kiocb *req, int ret) 98 { 99 int signo = 0; 100 101 if (ret > 0) { 102 signo = SIGCHLD; 103 ret = 0; 104 } 105 106 if (!io_waitid_copy_si(req, signo)) 107 ret = -EFAULT; 108 io_waitid_free(req); 109 return ret; 110 } 111 112 static void io_waitid_remove_wq(struct io_kiocb *req) 113 { 114 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 115 struct wait_queue_head *head; 116 117 head = smp_load_acquire(&iw->head); 118 if (head) { 119 struct io_waitid_async *iwa = req->async_data; 120 121 smp_store_release(&iw->head, NULL); 122 spin_lock_irq(&head->lock); 123 list_del_init(&iwa->wo.child_wait.entry); 124 spin_unlock_irq(&head->lock); 125 } 126 } 127 128 static void io_waitid_complete(struct io_kiocb *req, int ret, bool copy_si) 129 { 130 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 131 132 /* anyone completing better be holding a reference */ 133 WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK)); 134 135 lockdep_assert_held(&req->ctx->uring_lock); 136 137 hlist_del_init(&req->hash_node); 138 io_waitid_remove_wq(req); 139 140 if (copy_si) 141 ret = io_waitid_finish(req, ret); 142 else 143 io_waitid_free(req); 144 if (ret < 0) 145 req_set_fail(req); 146 io_req_set_res(req, ret, 0); 147 } 148 149 static bool __io_waitid_cancel(struct io_kiocb *req, bool copy_si) 150 { 151 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 152 153 lockdep_assert_held(&req->ctx->uring_lock); 154 155 /* 156 * Mark us canceled regardless of ownership. This will prevent a 157 * potential retry from a spurious wakeup. 158 */ 159 atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs); 160 161 /* claim ownership */ 162 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 163 return false; 164 165 io_waitid_complete(req, -ECANCELED, copy_si); 166 io_req_queue_tw_complete(req, -ECANCELED); 167 return true; 168 } 169 170 static bool io_waitid_cancel_cb(struct io_kiocb *req) 171 { 172 return __io_waitid_cancel(req, true); 173 } 174 175 static bool io_waitid_cancel_nocopy_cb(struct io_kiocb *req) 176 { 177 return __io_waitid_cancel(req, false); 178 } 179 180 int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, 181 unsigned int issue_flags) 182 { 183 return io_cancel_remove(ctx, cd, issue_flags, &ctx->waitid_list, io_waitid_cancel_cb); 184 } 185 186 bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx, 187 bool cancel_all) 188 { 189 return io_cancel_remove_all(ctx, tctx, &ctx->waitid_list, cancel_all, 190 tctx ? io_waitid_cancel_cb : io_waitid_cancel_nocopy_cb); 191 } 192 193 static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req) 194 { 195 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 196 197 if (!atomic_sub_return(1, &iw->refs)) 198 return false; 199 200 io_waitid_remove_wq(req); 201 202 /* 203 * Wakeup triggered, racing with us. It was prevented from 204 * completing because of that, queue up the tw to do that. 205 */ 206 req->io_task_work.func = io_waitid_cb; 207 io_req_task_work_add(req); 208 return true; 209 } 210 211 static void io_waitid_cb(struct io_tw_req tw_req, io_tw_token_t tw) 212 { 213 struct io_kiocb *req = tw_req.req; 214 struct io_waitid_async *iwa = req->async_data; 215 struct io_ring_ctx *ctx = req->ctx; 216 int ret; 217 218 io_tw_lock(ctx, tw); 219 if (unlikely(tw.cancel)) { 220 io_waitid_complete(req, -ECANCELED, false); 221 io_req_task_complete(tw_req, tw); 222 return; 223 } 224 225 ret = __do_wait(&iwa->wo); 226 227 /* 228 * If we get -ERESTARTSYS here, we need to re-arm and check again 229 * to ensure we get another callback. If the retry works, then we can 230 * just remove ourselves from the waitqueue again and finish the 231 * request. 232 */ 233 if (unlikely(ret == -ERESTARTSYS)) { 234 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 235 236 /* Don't retry if cancel found it meanwhile */ 237 ret = -ECANCELED; 238 if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) { 239 iw->head = ¤t->signal->wait_chldexit; 240 add_wait_queue(iw->head, &iwa->wo.child_wait); 241 ret = __do_wait(&iwa->wo); 242 if (ret == -ERESTARTSYS) { 243 /* retry armed, drop our ref */ 244 io_waitid_drop_issue_ref(req); 245 return; 246 } 247 /* fall through to complete, will kill waitqueue */ 248 } 249 } 250 251 io_waitid_complete(req, ret, true); 252 io_req_task_complete(tw_req, tw); 253 } 254 255 static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode, 256 int sync, void *key) 257 { 258 struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait); 259 struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo); 260 struct io_kiocb *req = iwa->req; 261 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 262 struct task_struct *p = key; 263 264 if (!pid_child_should_wake(wo, p)) 265 return 0; 266 267 list_del_init(&wait->entry); 268 smp_store_release(&iw->head, NULL); 269 270 /* cancel is in progress */ 271 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 272 return 1; 273 274 req->io_task_work.func = io_waitid_cb; 275 __io_req_task_work_add(req, IOU_F_TWQ_IN_WAKE); 276 return 1; 277 } 278 279 int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 280 { 281 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 282 struct io_waitid_async *iwa; 283 284 if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags) 285 return -EINVAL; 286 287 iwa = io_uring_alloc_async_data(NULL, req); 288 if (unlikely(!iwa)) 289 return -ENOMEM; 290 iwa->req = req; 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->head = NULL; 296 iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2)); 297 memset(&iw->info, 0, sizeof(iw->info)); 298 return 0; 299 } 300 301 int io_waitid(struct io_kiocb *req, unsigned int issue_flags) 302 { 303 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 304 struct io_waitid_async *iwa = req->async_data; 305 struct io_ring_ctx *ctx = req->ctx; 306 int ret; 307 308 ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info, 309 iw->options, NULL); 310 if (ret) 311 goto done; 312 313 /* 314 * Mark the request as busy upfront, in case we're racing with the 315 * wakeup. If we are, then we'll notice when we drop this initial 316 * reference again after arming. 317 */ 318 atomic_set(&iw->refs, 1); 319 320 /* 321 * Cancel must hold the ctx lock, so there's no risk of cancelation 322 * finding us until a) we remain on the list, and b) the lock is 323 * dropped. We only need to worry about racing with the wakeup 324 * callback. 325 */ 326 io_ring_submit_lock(ctx, issue_flags); 327 328 /* 329 * iw->head is valid under the ring lock, and as long as the request 330 * is on the waitid_list where cancelations may find it. 331 */ 332 iw->head = ¤t->signal->wait_chldexit; 333 hlist_add_head(&req->hash_node, &ctx->waitid_list); 334 335 init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait); 336 iwa->wo.child_wait.private = req->tctx->task; 337 add_wait_queue(iw->head, &iwa->wo.child_wait); 338 339 ret = __do_wait(&iwa->wo); 340 if (ret == -ERESTARTSYS) { 341 /* 342 * Nobody else grabbed a reference, it'll complete when we get 343 * a waitqueue callback, or if someone cancels it. 344 */ 345 if (!io_waitid_drop_issue_ref(req)) { 346 io_ring_submit_unlock(ctx, issue_flags); 347 return IOU_ISSUE_SKIP_COMPLETE; 348 } 349 350 /* 351 * Wakeup triggered, racing with us. It was prevented from 352 * completing because of that, queue up the tw to do that. 353 */ 354 io_ring_submit_unlock(ctx, issue_flags); 355 return IOU_ISSUE_SKIP_COMPLETE; 356 } 357 358 hlist_del_init(&req->hash_node); 359 io_waitid_remove_wq(req); 360 ret = io_waitid_finish(req, ret); 361 362 io_ring_submit_unlock(ctx, issue_flags); 363 done: 364 if (ret < 0) 365 req_set_fail(req); 366 io_req_set_res(req, ret, 0); 367 return IOU_COMPLETE; 368 } 369