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 = READ_ONCE(iw->head); 118 if (head) { 119 struct io_waitid_async *iwa = req->async_data; 120 121 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) 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 ret = io_waitid_finish(req, ret); 141 if (ret < 0) 142 req_set_fail(req); 143 io_req_set_res(req, ret, 0); 144 } 145 146 static bool __io_waitid_cancel(struct io_kiocb *req) 147 { 148 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 149 150 lockdep_assert_held(&req->ctx->uring_lock); 151 152 /* 153 * Mark us canceled regardless of ownership. This will prevent a 154 * potential retry from a spurious wakeup. 155 */ 156 atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs); 157 158 /* claim ownership */ 159 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 160 return false; 161 162 io_waitid_complete(req, -ECANCELED); 163 io_req_queue_tw_complete(req, -ECANCELED); 164 return true; 165 } 166 167 int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, 168 unsigned int issue_flags) 169 { 170 return io_cancel_remove(ctx, cd, issue_flags, &ctx->waitid_list, __io_waitid_cancel); 171 } 172 173 bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx, 174 bool cancel_all) 175 { 176 return io_cancel_remove_all(ctx, tctx, &ctx->waitid_list, cancel_all, __io_waitid_cancel); 177 } 178 179 static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req) 180 { 181 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 182 183 if (!atomic_sub_return(1, &iw->refs)) 184 return false; 185 186 io_waitid_remove_wq(req); 187 188 /* 189 * Wakeup triggered, racing with us. It was prevented from 190 * completing because of that, queue up the tw to do that. 191 */ 192 req->io_task_work.func = io_waitid_cb; 193 io_req_task_work_add(req); 194 return true; 195 } 196 197 static void io_waitid_cb(struct io_tw_req tw_req, io_tw_token_t tw) 198 { 199 struct io_kiocb *req = tw_req.req; 200 struct io_waitid_async *iwa = req->async_data; 201 struct io_ring_ctx *ctx = req->ctx; 202 int ret; 203 204 io_tw_lock(ctx, tw); 205 206 ret = __do_wait(&iwa->wo); 207 208 /* 209 * If we get -ERESTARTSYS here, we need to re-arm and check again 210 * to ensure we get another callback. If the retry works, then we can 211 * just remove ourselves from the waitqueue again and finish the 212 * request. 213 */ 214 if (unlikely(ret == -ERESTARTSYS)) { 215 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 216 217 /* Don't retry if cancel found it meanwhile */ 218 ret = -ECANCELED; 219 if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) { 220 iw->head = ¤t->signal->wait_chldexit; 221 add_wait_queue(iw->head, &iwa->wo.child_wait); 222 ret = __do_wait(&iwa->wo); 223 if (ret == -ERESTARTSYS) { 224 /* retry armed, drop our ref */ 225 io_waitid_drop_issue_ref(req); 226 return; 227 } 228 /* fall through to complete, will kill waitqueue */ 229 } 230 } 231 232 io_waitid_complete(req, ret); 233 io_req_task_complete(tw_req, tw); 234 } 235 236 static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode, 237 int sync, void *key) 238 { 239 struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait); 240 struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo); 241 struct io_kiocb *req = iwa->req; 242 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 243 struct task_struct *p = key; 244 245 if (!pid_child_should_wake(wo, p)) 246 return 0; 247 248 list_del_init(&wait->entry); 249 iw->head = NULL; 250 251 /* cancel is in progress */ 252 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 253 return 1; 254 255 req->io_task_work.func = io_waitid_cb; 256 io_req_task_work_add(req); 257 return 1; 258 } 259 260 int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 261 { 262 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 263 struct io_waitid_async *iwa; 264 265 if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags) 266 return -EINVAL; 267 268 iwa = io_uring_alloc_async_data(NULL, req); 269 if (unlikely(!iwa)) 270 return -ENOMEM; 271 iwa->req = req; 272 273 iw->which = READ_ONCE(sqe->len); 274 iw->upid = READ_ONCE(sqe->fd); 275 iw->options = READ_ONCE(sqe->file_index); 276 iw->head = NULL; 277 iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2)); 278 return 0; 279 } 280 281 int io_waitid(struct io_kiocb *req, unsigned int issue_flags) 282 { 283 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 284 struct io_waitid_async *iwa = req->async_data; 285 struct io_ring_ctx *ctx = req->ctx; 286 int ret; 287 288 ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info, 289 iw->options, NULL); 290 if (ret) 291 goto done; 292 293 /* 294 * Mark the request as busy upfront, in case we're racing with the 295 * wakeup. If we are, then we'll notice when we drop this initial 296 * reference again after arming. 297 */ 298 atomic_set(&iw->refs, 1); 299 300 /* 301 * Cancel must hold the ctx lock, so there's no risk of cancelation 302 * finding us until a) we remain on the list, and b) the lock is 303 * dropped. We only need to worry about racing with the wakeup 304 * callback. 305 */ 306 io_ring_submit_lock(ctx, issue_flags); 307 308 /* 309 * iw->head is valid under the ring lock, and as long as the request 310 * is on the waitid_list where cancelations may find it. 311 */ 312 iw->head = ¤t->signal->wait_chldexit; 313 hlist_add_head(&req->hash_node, &ctx->waitid_list); 314 315 init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait); 316 iwa->wo.child_wait.private = req->tctx->task; 317 add_wait_queue(iw->head, &iwa->wo.child_wait); 318 319 ret = __do_wait(&iwa->wo); 320 if (ret == -ERESTARTSYS) { 321 /* 322 * Nobody else grabbed a reference, it'll complete when we get 323 * a waitqueue callback, or if someone cancels it. 324 */ 325 if (!io_waitid_drop_issue_ref(req)) { 326 io_ring_submit_unlock(ctx, issue_flags); 327 return IOU_ISSUE_SKIP_COMPLETE; 328 } 329 330 /* 331 * Wakeup triggered, racing with us. It was prevented from 332 * completing because of that, queue up the tw to do that. 333 */ 334 io_ring_submit_unlock(ctx, issue_flags); 335 return IOU_ISSUE_SKIP_COMPLETE; 336 } 337 338 hlist_del_init(&req->hash_node); 339 io_waitid_remove_wq(req); 340 ret = io_waitid_finish(req, ret); 341 342 io_ring_submit_unlock(ctx, issue_flags); 343 done: 344 if (ret < 0) 345 req_set_fail(req); 346 io_req_set_res(req, ret, 0); 347 return IOU_COMPLETE; 348 } 349