// SPDX-License-Identifier: GPL-2.0/* * Support for async notification of waitid */#include <linux/kernel.h>#include <linux/errno.h>#include <linux/fs.h>#include <linux/file.h>#include <linux/compat.h>#include <linux/io_uring.h> #include <uapi/linux/io_uring.h> #include "io_uring.h"#include "cancel.h"#include "waitid.h"#include "../kernel/exit.h" static void io_waitid_cb(struct io_tw_req tw_req, io_tw_token_t tw); #define IO_WAITID_CANCEL_FLAG	BIT(31)#define IO_WAITID_REF_MASK	GENMASK(30, 0) struct io_waitid {	struct file *file;	int which;	pid_t upid;	int options;	atomic_t refs;	struct wait_queue_head *head;	struct siginfo __user *infop;	struct waitid_info info;}; static void io_waitid_free(struct io_kiocb *req){	struct io_waitid_async *iwa = req->async_data; 	put_pid(iwa->wo.wo_pid);	io_req_async_data_free(req);} static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo){	struct compat_siginfo __user *infop;	bool ret; 	infop = (struct compat_siginfo __user *) iw->infop; 	if (!user_write_access_begin(infop, sizeof(*infop)))		return false; 	unsafe_put_user(signo, &infop->si_signo, Efault);	unsafe_put_user(0, &infop->si_errno, Efault);	unsafe_put_user(iw->info.cause, &infop->si_code, Efault);	unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);	unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);	unsafe_put_user(iw->info.status, &infop->si_status, Efault);	ret = true;done:	user_write_access_end();	return ret;Efault:	ret = false;	goto done;} static bool io_waitid_copy_si(struct io_kiocb *req, int signo){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);	bool ret; 	if (!iw->infop)		return true; 	if (io_is_compat(req->ctx))		return io_waitid_compat_copy_si(iw, signo); 	if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))		return false; 	unsafe_put_user(signo, &iw->infop->si_signo, Efault);	unsafe_put_user(0, &iw->infop->si_errno, Efault);	unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);	unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);	unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);	unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);	ret = true;done:	user_write_access_end();	return ret;Efault:	ret = false;	goto done;} static int io_waitid_finish(struct io_kiocb *req, int ret){	int signo = 0; 	if (ret > 0) {		signo = SIGCHLD;		ret = 0;	} 	if (!io_waitid_copy_si(req, signo))		ret = -EFAULT;	io_waitid_free(req);	return ret;} static void io_waitid_remove_wq(struct io_kiocb *req){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);	struct wait_queue_head *head; 	head = smp_load_acquire(&iw->head);	if (head) {		struct io_waitid_async *iwa = req->async_data; 		smp_store_release(&iw->head, NULL);		spin_lock_irq(&head->lock);		list_del_init(&iwa->wo.child_wait.entry);		spin_unlock_irq(&head->lock);	}} static void io_waitid_complete(struct io_kiocb *req, int ret, bool copy_si){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 	/* anyone completing better be holding a reference */	WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK)); 	lockdep_assert_held(&req->ctx->uring_lock); 	hlist_del_init(&req->hash_node);	io_waitid_remove_wq(req); 	if (copy_si)		ret = io_waitid_finish(req, ret);	else		io_waitid_free(req);	if (ret < 0)		req_set_fail(req);	io_req_set_res(req, ret, 0);} static bool __io_waitid_cancel(struct io_kiocb *req, bool copy_si){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 	lockdep_assert_held(&req->ctx->uring_lock); 	/*	 * Mark us canceled regardless of ownership. This will prevent a	 * potential retry from a spurious wakeup.	 */	atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs); 	/* claim ownership */	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)		return false; 	io_waitid_complete(req, -ECANCELED, copy_si);	io_req_queue_tw_complete(req, -ECANCELED);	return true;} static bool io_waitid_cancel_cb(struct io_kiocb *req){	return __io_waitid_cancel(req, true);} static bool io_waitid_cancel_nocopy_cb(struct io_kiocb *req){	return __io_waitid_cancel(req, false);} int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,		     unsigned int issue_flags){	return io_cancel_remove(ctx, cd, issue_flags, &ctx->waitid_list, io_waitid_cancel_cb);} bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx,			  bool cancel_all){	return io_cancel_remove_all(ctx, tctx, &ctx->waitid_list, cancel_all,				       tctx ? io_waitid_cancel_cb : io_waitid_cancel_nocopy_cb);} static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 	if (!atomic_sub_return(1, &iw->refs))		return false; 	io_waitid_remove_wq(req); 	/*	 * Wakeup triggered, racing with us. It was prevented from	 * completing because of that, queue up the tw to do that.	 */	req->io_task_work.func = io_waitid_cb;	io_req_task_work_add(req);	return true;} static void io_waitid_cb(struct io_tw_req tw_req, io_tw_token_t tw){	struct io_kiocb *req = tw_req.req;	struct io_waitid_async *iwa = req->async_data;	struct io_ring_ctx *ctx = req->ctx;	int ret; 	io_tw_lock(ctx, tw);	if (unlikely(tw.cancel)) {		io_waitid_complete(req, -ECANCELED, false);		io_req_task_complete(tw_req, tw);		return;	} 	ret = __do_wait(&iwa->wo); 	/*	 * If we get -ERESTARTSYS here, we need to re-arm and check again	 * to ensure we get another callback. If the retry works, then we can	 * just remove ourselves from the waitqueue again and finish the	 * request.	 */	if (unlikely(ret == -ERESTARTSYS)) {		struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid); 		/* Don't retry if cancel found it meanwhile */		ret = -ECANCELED;		if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {			iw->head = &current->signal->wait_chldexit;			add_wait_queue(iw->head, &iwa->wo.child_wait);			ret = __do_wait(&iwa->wo);			if (ret == -ERESTARTSYS) {				/* retry armed, drop our ref */				io_waitid_drop_issue_ref(req);				return;			}			/* fall through to complete, will kill waitqueue */		}	} 	io_waitid_complete(req, ret, true);	io_req_task_complete(tw_req, tw);} static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,			  int sync, void *key){	struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);	struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);	struct io_kiocb *req = iwa->req;	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);	struct task_struct *p = key; 	if (!pid_child_should_wake(wo, p))		return 0; 	list_del_init(&wait->entry);	smp_store_release(&iw->head, NULL); 	/* cancel is in progress */	if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)		return 1; 	req->io_task_work.func = io_waitid_cb;	__io_req_task_work_add(req, IOU_F_TWQ_IN_WAKE);	return 1;} int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);	struct io_waitid_async *iwa; 	if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)		return -EINVAL; 	iwa = io_uring_alloc_async_data(NULL, req);	if (unlikely(!iwa))		return -ENOMEM;	iwa->req = req; 	iw->which = READ_ONCE(sqe->len);	iw->upid = READ_ONCE(sqe->fd);	iw->options = READ_ONCE(sqe->file_index);	iw->head = NULL;	iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));	memset(&iw->info, 0, sizeof(iw->info));	return 0;} int io_waitid(struct io_kiocb *req, unsigned int issue_flags){	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);	struct io_waitid_async *iwa = req->async_data;	struct io_ring_ctx *ctx = req->ctx;	int ret; 	ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,					iw->options, NULL);	if (ret)		goto done; 	/*	 * Mark the request as busy upfront, in case we're racing with the	 * wakeup. If we are, then we'll notice when we drop this initial	 * reference again after arming.	 */	atomic_set(&iw->refs, 1); 	/*	 * Cancel must hold the ctx lock, so there's no risk of cancelation	 * finding us until a) we remain on the list, and b) the lock is	 * dropped. We only need to worry about racing with the wakeup	 * callback.	 */	io_ring_submit_lock(ctx, issue_flags); 	/*	 * iw->head is valid under the ring lock, and as long as the request	 * is on the waitid_list where cancelations may find it.	 */	iw->head = &current->signal->wait_chldexit;	hlist_add_head(&req->hash_node, &ctx->waitid_list); 	init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);	iwa->wo.child_wait.private = req->tctx->task;	add_wait_queue(iw->head, &iwa->wo.child_wait); 	ret = __do_wait(&iwa->wo);	if (ret == -ERESTARTSYS) {		/*		 * Nobody else grabbed a reference, it'll complete when we get		 * a waitqueue callback, or if someone cancels it.		 */		if (!io_waitid_drop_issue_ref(req)) {			io_ring_submit_unlock(ctx, issue_flags);			return IOU_ISSUE_SKIP_COMPLETE;		} 		/*		 * Wakeup triggered, racing with us. It was prevented from		 * completing because of that, queue up the tw to do that.		 */		io_ring_submit_unlock(ctx, issue_flags);		return IOU_ISSUE_SKIP_COMPLETE;	} 	hlist_del_init(&req->hash_node);	io_waitid_remove_wq(req);	ret = io_waitid_finish(req, ret); 	io_ring_submit_unlock(ctx, issue_flags);done:	if (ret < 0)		req_set_fail(req);	io_req_set_res(req, ret, 0);	return IOU_COMPLETE;}