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, 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 kfree(req->async_data); 41 req->async_data = NULL; 42 req->flags &= ~REQ_F_ASYNC_DATA; 43 } 44 45 static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo) 46 { 47 struct compat_siginfo __user *infop; 48 bool ret; 49 50 infop = (struct compat_siginfo __user *) iw->infop; 51 52 if (!user_write_access_begin(infop, sizeof(*infop))) 53 return false; 54 55 unsafe_put_user(signo, &infop->si_signo, Efault); 56 unsafe_put_user(0, &infop->si_errno, Efault); 57 unsafe_put_user(iw->info.cause, &infop->si_code, Efault); 58 unsafe_put_user(iw->info.pid, &infop->si_pid, Efault); 59 unsafe_put_user(iw->info.uid, &infop->si_uid, Efault); 60 unsafe_put_user(iw->info.status, &infop->si_status, Efault); 61 ret = true; 62 done: 63 user_write_access_end(); 64 return ret; 65 Efault: 66 ret = false; 67 goto done; 68 } 69 70 static bool io_waitid_copy_si(struct io_kiocb *req, int signo) 71 { 72 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 73 bool ret; 74 75 if (!iw->infop) 76 return true; 77 78 if (io_is_compat(req->ctx)) 79 return io_waitid_compat_copy_si(iw, signo); 80 81 if (!user_write_access_begin(iw->infop, sizeof(*iw->infop))) 82 return false; 83 84 unsafe_put_user(signo, &iw->infop->si_signo, Efault); 85 unsafe_put_user(0, &iw->infop->si_errno, Efault); 86 unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault); 87 unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault); 88 unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault); 89 unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault); 90 ret = true; 91 done: 92 user_write_access_end(); 93 return ret; 94 Efault: 95 ret = false; 96 goto done; 97 } 98 99 static int io_waitid_finish(struct io_kiocb *req, int ret) 100 { 101 int signo = 0; 102 103 if (ret > 0) { 104 signo = SIGCHLD; 105 ret = 0; 106 } 107 108 if (!io_waitid_copy_si(req, signo)) 109 ret = -EFAULT; 110 io_waitid_free(req); 111 return ret; 112 } 113 114 static void io_waitid_complete(struct io_kiocb *req, int ret) 115 { 116 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 117 118 /* anyone completing better be holding a reference */ 119 WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK)); 120 121 lockdep_assert_held(&req->ctx->uring_lock); 122 123 hlist_del_init(&req->hash_node); 124 125 ret = io_waitid_finish(req, ret); 126 if (ret < 0) 127 req_set_fail(req); 128 io_req_set_res(req, ret, 0); 129 } 130 131 static bool __io_waitid_cancel(struct io_kiocb *req) 132 { 133 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 134 struct io_waitid_async *iwa = req->async_data; 135 136 /* 137 * Mark us canceled regardless of ownership. This will prevent a 138 * potential retry from a spurious wakeup. 139 */ 140 atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs); 141 142 /* claim ownership */ 143 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 144 return false; 145 146 spin_lock_irq(&iw->head->lock); 147 list_del_init(&iwa->wo.child_wait.entry); 148 spin_unlock_irq(&iw->head->lock); 149 io_waitid_complete(req, -ECANCELED); 150 io_req_queue_tw_complete(req, -ECANCELED); 151 return true; 152 } 153 154 int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, 155 unsigned int issue_flags) 156 { 157 return io_cancel_remove(ctx, cd, issue_flags, &ctx->waitid_list, __io_waitid_cancel); 158 } 159 160 bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx, 161 bool cancel_all) 162 { 163 return io_cancel_remove_all(ctx, tctx, &ctx->waitid_list, cancel_all, __io_waitid_cancel); 164 } 165 166 static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req) 167 { 168 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 169 struct io_waitid_async *iwa = req->async_data; 170 171 if (!atomic_sub_return(1, &iw->refs)) 172 return false; 173 174 /* 175 * Wakeup triggered, racing with us. It was prevented from 176 * completing because of that, queue up the tw to do that. 177 */ 178 req->io_task_work.func = io_waitid_cb; 179 io_req_task_work_add(req); 180 remove_wait_queue(iw->head, &iwa->wo.child_wait); 181 return true; 182 } 183 184 static void io_waitid_cb(struct io_kiocb *req, io_tw_token_t tw) 185 { 186 struct io_waitid_async *iwa = req->async_data; 187 struct io_ring_ctx *ctx = req->ctx; 188 int ret; 189 190 io_tw_lock(ctx, tw); 191 192 ret = __do_wait(&iwa->wo); 193 194 /* 195 * If we get -ERESTARTSYS here, we need to re-arm and check again 196 * to ensure we get another callback. If the retry works, then we can 197 * just remove ourselves from the waitqueue again and finish the 198 * request. 199 */ 200 if (unlikely(ret == -ERESTARTSYS)) { 201 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 202 203 /* Don't retry if cancel found it meanwhile */ 204 ret = -ECANCELED; 205 if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) { 206 iw->head = ¤t->signal->wait_chldexit; 207 add_wait_queue(iw->head, &iwa->wo.child_wait); 208 ret = __do_wait(&iwa->wo); 209 if (ret == -ERESTARTSYS) { 210 /* retry armed, drop our ref */ 211 io_waitid_drop_issue_ref(req); 212 return; 213 } 214 215 remove_wait_queue(iw->head, &iwa->wo.child_wait); 216 } 217 } 218 219 io_waitid_complete(req, ret); 220 io_req_task_complete(req, tw); 221 } 222 223 static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode, 224 int sync, void *key) 225 { 226 struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait); 227 struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo); 228 struct io_kiocb *req = iwa->req; 229 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 230 struct task_struct *p = key; 231 232 if (!pid_child_should_wake(wo, p)) 233 return 0; 234 235 /* cancel is in progress */ 236 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK) 237 return 1; 238 239 req->io_task_work.func = io_waitid_cb; 240 io_req_task_work_add(req); 241 list_del_init(&wait->entry); 242 return 1; 243 } 244 245 int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 246 { 247 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 248 struct io_waitid_async *iwa; 249 250 if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags) 251 return -EINVAL; 252 253 iwa = io_uring_alloc_async_data(NULL, req); 254 if (!unlikely(iwa)) 255 return -ENOMEM; 256 iwa->req = req; 257 258 iw->which = READ_ONCE(sqe->len); 259 iw->upid = READ_ONCE(sqe->fd); 260 iw->options = READ_ONCE(sqe->file_index); 261 iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2)); 262 return 0; 263 } 264 265 int io_waitid(struct io_kiocb *req, unsigned int issue_flags) 266 { 267 struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 268 struct io_waitid_async *iwa = req->async_data; 269 struct io_ring_ctx *ctx = req->ctx; 270 int ret; 271 272 ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info, 273 iw->options, NULL); 274 if (ret) 275 goto done; 276 277 /* 278 * Mark the request as busy upfront, in case we're racing with the 279 * wakeup. If we are, then we'll notice when we drop this initial 280 * reference again after arming. 281 */ 282 atomic_set(&iw->refs, 1); 283 284 /* 285 * Cancel must hold the ctx lock, so there's no risk of cancelation 286 * finding us until a) we remain on the list, and b) the lock is 287 * dropped. We only need to worry about racing with the wakeup 288 * callback. 289 */ 290 io_ring_submit_lock(ctx, issue_flags); 291 hlist_add_head(&req->hash_node, &ctx->waitid_list); 292 293 init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait); 294 iwa->wo.child_wait.private = req->tctx->task; 295 iw->head = ¤t->signal->wait_chldexit; 296 add_wait_queue(iw->head, &iwa->wo.child_wait); 297 298 ret = __do_wait(&iwa->wo); 299 if (ret == -ERESTARTSYS) { 300 /* 301 * Nobody else grabbed a reference, it'll complete when we get 302 * a waitqueue callback, or if someone cancels it. 303 */ 304 if (!io_waitid_drop_issue_ref(req)) { 305 io_ring_submit_unlock(ctx, issue_flags); 306 return IOU_ISSUE_SKIP_COMPLETE; 307 } 308 309 /* 310 * Wakeup triggered, racing with us. It was prevented from 311 * completing because of that, queue up the tw to do that. 312 */ 313 io_ring_submit_unlock(ctx, issue_flags); 314 return IOU_ISSUE_SKIP_COMPLETE; 315 } 316 317 hlist_del_init(&req->hash_node); 318 remove_wait_queue(iw->head, &iwa->wo.child_wait); 319 ret = io_waitid_finish(req, ret); 320 321 io_ring_submit_unlock(ctx, issue_flags); 322 done: 323 if (ret < 0) 324 req_set_fail(req); 325 io_req_set_res(req, ret, 0); 326 return IOU_OK; 327 } 328