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1// SPDX-License-Identifier: GPL-2.02/*3 * Support for async notification of waitid4 */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(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_COMPAT46static 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#endif71 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_COMPAT81 if (req->ctx->compat)82 return io_waitid_compat_copy_si(iw, signo);83#endif84 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 = {};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(&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, ret, 0);134 io_req_task_complete(req, &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 a144 * potential retry from a spurious wakeup.145 */146 atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs);147 148 /* claim ownership */149 if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)150 return false;151 152 spin_lock_irq(&iw->head->lock);153 list_del_init(&iwa->wo.child_wait.entry);154 spin_unlock_irq(&iw->head->lock);155 io_waitid_complete(req, -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(req, task, cancel_all))198 continue;199 hlist_del_init(&req->hash_node);200 __io_waitid_cancel(ctx, req);201 found = true;202 }203 204 return found;205}206 207static HWJS_SUSPENDS 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(1, &iw->refs))213 return false;214 215 /*216 * Wakeup triggered, racing with us. It was prevented from217 * 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(iw->head, &iwa->wo.child_wait);222 return true;223}224 225static HWJS_SUSPENDS 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(&iwa->wo);234 235 /*236 * If we get -ERESTARTSYS here, we need to re-arm and check again237 * to ensure we get another callback. If the retry works, then we can238 * just remove ourselves from the waitqueue again and finish the239 * 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(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {247 iw->head = ¤t->signal->wait_chldexit;248 add_wait_queue(iw->head, &iwa->wo.child_wait);249 ret = __do_wait(&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(iw->head, &iwa->wo.child_wait);257 }258 }259 260 io_waitid_complete(req, ret);261}262 263static HWJS_SUSPENDS 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(&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(&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(&iwa->wo, iw->which, iw->upid, &iw->info,313 iw->options, NULL);314 if (ret)315 goto done;316 317 /*318 * Mark the request as busy upfront, in case we're racing with the319 * wakeup. If we are, then we'll notice when we drop this initial320 * reference again after arming.321 */322 atomic_set(&iw->refs, 1);323 324 /*325 * Cancel must hold the ctx lock, so there's no risk of cancelation326 * finding us until a) we remain on the list, and b) the lock is327 * dropped. We only need to worry about racing with the wakeup328 * callback.329 */330 io_ring_submit_lock(ctx, issue_flags);331 hlist_add_head(&req->hash_node, &ctx->waitid_list);332 333 init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);334 iwa->wo.child_wait.private = req->task;335 iw->head = ¤t->signal->wait_chldexit;336 add_wait_queue(iw->head, &iwa->wo.child_wait);337 338 ret = __do_wait(&iwa->wo);339 if (ret == -ERESTARTSYS) {340 /*341 * Nobody else grabbed a reference, it'll complete when we get342 * 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 from351 * 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(&req->hash_node);358 remove_wait_queue(iw->head, &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, ret, 0);366 return IOU_OK;367}368