--- /dev/null
+// 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_kiocb *req, struct io_tw_state *ts);
+
+#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);
+ kfree(req->async_data);
+ req->async_data = NULL;
+ req->flags &= ~REQ_F_ASYNC_DATA;
+}
+
+#ifdef CONFIG_COMPAT
+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;
+}
+#endif
+
+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;
+
+#ifdef CONFIG_COMPAT
+ if (req->ctx->compat)
+ return io_waitid_compat_copy_si(iw, signo);
+#endif
+
+ 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_complete(struct io_kiocb *req, int ret)
+{
+ struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+ struct io_tw_state ts = { .locked = true };
+
+ /* 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);
+
+ /*
+ * Did cancel find it meanwhile?
+ */
+ if (hlist_unhashed(&req->hash_node))
+ return;
+
+ hlist_del_init(&req->hash_node);
+
+ ret = io_waitid_finish(req, ret);
+ if (ret < 0)
+ req_set_fail(req);
+ io_req_set_res(req, ret, 0);
+ io_req_task_complete(req, &ts);
+}
+
+static bool __io_waitid_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)
+{
+ struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+ struct io_waitid_async *iwa = req->async_data;
+
+ /*
+ * 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;
+
+ spin_lock_irq(&iw->head->lock);
+ list_del_init(&iwa->wo.child_wait.entry);
+ spin_unlock_irq(&iw->head->lock);
+ io_waitid_complete(req, -ECANCELED);
+ return true;
+}
+
+int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
+ unsigned int issue_flags)
+{
+ struct hlist_node *tmp;
+ struct io_kiocb *req;
+ int nr = 0;
+
+ if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_FD_FIXED))
+ return -ENOENT;
+
+ io_ring_submit_lock(ctx, issue_flags);
+ hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
+ if (req->cqe.user_data != cd->data &&
+ !(cd->flags & IORING_ASYNC_CANCEL_ANY))
+ continue;
+ if (__io_waitid_cancel(ctx, req))
+ nr++;
+ if (!(cd->flags & IORING_ASYNC_CANCEL_ALL))
+ break;
+ }
+ io_ring_submit_unlock(ctx, issue_flags);
+
+ if (nr)
+ return nr;
+
+ return -ENOENT;
+}
+
+bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
+ bool cancel_all)
+{
+ struct hlist_node *tmp;
+ struct io_kiocb *req;
+ bool found = false;
+
+ lockdep_assert_held(&ctx->uring_lock);
+
+ hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
+ if (!io_match_task_safe(req, task, cancel_all))
+ continue;
+ __io_waitid_cancel(ctx, req);
+ found = true;
+ }
+
+ return found;
+}
+
+static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
+{
+ struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+ struct io_waitid_async *iwa = req->async_data;
+
+ if (!atomic_sub_return(1, &iw->refs))
+ return false;
+
+ /*
+ * 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);
+ remove_wait_queue(iw->head, &iwa->wo.child_wait);
+ return true;
+}
+
+static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts)
+{
+ struct io_waitid_async *iwa = req->async_data;
+ struct io_ring_ctx *ctx = req->ctx;
+ int ret;
+
+ io_tw_lock(ctx, ts);
+
+ 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 = ¤t->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;
+ }
+
+ remove_wait_queue(iw->head, &iwa->wo.child_wait);
+ }
+ }
+
+ io_waitid_complete(req, ret);
+}
+
+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;
+
+ /* 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);
+ list_del_init(&wait->entry);
+ 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);
+
+ if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
+ return -EINVAL;
+
+ iw->which = READ_ONCE(sqe->len);
+ iw->upid = READ_ONCE(sqe->fd);
+ iw->options = READ_ONCE(sqe->file_index);
+ iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+ 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_ring_ctx *ctx = req->ctx;
+ struct io_waitid_async *iwa;
+ int ret;
+
+ if (io_alloc_async_data(req))
+ return -ENOMEM;
+
+ iwa = req->async_data;
+ iwa->req = req;
+
+ 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);
+ 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->task;
+ iw->head = ¤t->signal->wait_chldexit;
+ 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);
+ remove_wait_queue(iw->head, &iwa->wo.child_wait);
+ 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_OK;
+}
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