1 files changed, 298 insertions, 0 deletions
diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
new file mode 100644
index 0000000000..cd6dcf634b
--- /dev/null
+++ b/io_uring/msg_ring.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/nospec.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "rsrc.h"
+#include "filetable.h"
+#include "msg_ring.h"
+
+
+/* All valid masks for MSG_RING */
+#define IORING_MSG_RING_MASK		(IORING_MSG_RING_CQE_SKIP | \
+					IORING_MSG_RING_FLAGS_PASS)
+
+struct io_msg {
+	struct file			*file;
+	struct file			*src_file;
+	struct callback_head		tw;
+	u64 user_data;
+	u32 len;
+	u32 cmd;
+	u32 src_fd;
+	union {
+		u32 dst_fd;
+		u32 cqe_flags;
+	};
+	u32 flags;
+};
+
+static void io_double_unlock_ctx(struct io_ring_ctx *octx)
+{
+	mutex_unlock(&octx->uring_lock);
+}
+
+static int io_double_lock_ctx(struct io_ring_ctx *octx,
+			      unsigned int issue_flags)
+{
+	/*
+	 * To ensure proper ordering between the two ctxs, we can only
+	 * attempt a trylock on the target. If that fails and we already have
+	 * the source ctx lock, punt to io-wq.
+	 */
+	if (!(issue_flags & IO_URING_F_UNLOCKED)) {
+		if (!mutex_trylock(&octx->uring_lock))
+			return -EAGAIN;
+		return 0;
+	}
+	mutex_lock(&octx->uring_lock);
+	return 0;
+}
+
+void io_msg_ring_cleanup(struct io_kiocb *req)
+{
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+
+	if (WARN_ON_ONCE(!msg->src_file))
+		return;
+
+	fput(msg->src_file);
+	msg->src_file = NULL;
+}
+
+static inline bool io_msg_need_remote(struct io_ring_ctx *target_ctx)
+{
+	if (!target_ctx->task_complete)
+		return false;
+	return current != target_ctx->submitter_task;
+}
+
+static int io_msg_exec_remote(struct io_kiocb *req, task_work_func_t func)
+{
+	struct io_ring_ctx *ctx = req->file->private_data;
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+	struct task_struct *task = READ_ONCE(ctx->submitter_task);
+
+	if (unlikely(!task))
+		return -EOWNERDEAD;
+
+	init_task_work(&msg->tw, func);
+	if (task_work_add(ctx->submitter_task, &msg->tw, TWA_SIGNAL))
+		return -EOWNERDEAD;
+
+	return IOU_ISSUE_SKIP_COMPLETE;
+}
+
+static void io_msg_tw_complete(struct callback_head *head)
+{
+	struct io_msg *msg = container_of(head, struct io_msg, tw);
+	struct io_kiocb *req = cmd_to_io_kiocb(msg);
+	struct io_ring_ctx *target_ctx = req->file->private_data;
+	int ret = 0;
+
+	if (current->flags & PF_EXITING) {
+		ret = -EOWNERDEAD;
+	} else {
+		u32 flags = 0;
+
+		if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
+			flags = msg->cqe_flags;
+
+		/*
+		 * If the target ring is using IOPOLL mode, then we need to be
+		 * holding the uring_lock for posting completions. Other ring
+		 * types rely on the regular completion locking, which is
+		 * handled while posting.
+		 */
+		if (target_ctx->flags & IORING_SETUP_IOPOLL)
+			mutex_lock(&target_ctx->uring_lock);
+		if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
+			ret = -EOVERFLOW;
+		if (target_ctx->flags & IORING_SETUP_IOPOLL)
+			mutex_unlock(&target_ctx->uring_lock);
+	}
+
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_queue_tw_complete(req, ret);
+}
+
+static int io_msg_ring_data(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_ring_ctx *target_ctx = req->file->private_data;
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+	u32 flags = 0;
+	int ret;
+
+	if (msg->src_fd || msg->flags & ~IORING_MSG_RING_FLAGS_PASS)
+		return -EINVAL;
+	if (!(msg->flags & IORING_MSG_RING_FLAGS_PASS) && msg->dst_fd)
+		return -EINVAL;
+	if (target_ctx->flags & IORING_SETUP_R_DISABLED)
+		return -EBADFD;
+
+	if (io_msg_need_remote(target_ctx))
+		return io_msg_exec_remote(req, io_msg_tw_complete);
+
+	if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
+		flags = msg->cqe_flags;
+
+	ret = -EOVERFLOW;
+	if (target_ctx->flags & IORING_SETUP_IOPOLL) {
+		if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
+			return -EAGAIN;
+		if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
+			ret = 0;
+		io_double_unlock_ctx(target_ctx);
+	} else {
+		if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
+			ret = 0;
+	}
+	return ret;
+}
+
+static struct file *io_msg_grab_file(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct file *file = NULL;
+	int idx = msg->src_fd;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	if (likely(idx < ctx->nr_user_files)) {
+		idx = array_index_nospec(idx, ctx->nr_user_files);
+		file = io_file_from_index(&ctx->file_table, idx);
+		if (file)
+			get_file(file);
+	}
+	io_ring_submit_unlock(ctx, issue_flags);
+	return file;
+}
+
+static int io_msg_install_complete(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_ring_ctx *target_ctx = req->file->private_data;
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+	struct file *src_file = msg->src_file;
+	int ret;
+
+	if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
+		return -EAGAIN;
+
+	ret = __io_fixed_fd_install(target_ctx, src_file, msg->dst_fd);
+	if (ret < 0)
+		goto out_unlock;
+
+	msg->src_file = NULL;
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+
+	if (msg->flags & IORING_MSG_RING_CQE_SKIP)
+		goto out_unlock;
+	/*
+	 * If this fails, the target still received the file descriptor but
+	 * wasn't notified of the fact. This means that if this request
+	 * completes with -EOVERFLOW, then the sender must ensure that a
+	 * later IORING_OP_MSG_RING delivers the message.
+	 */
+	if (!io_post_aux_cqe(target_ctx, msg->user_data, ret, 0))
+		ret = -EOVERFLOW;
+out_unlock:
+	io_double_unlock_ctx(target_ctx);
+	return ret;
+}
+
+static void io_msg_tw_fd_complete(struct callback_head *head)
+{
+	struct io_msg *msg = container_of(head, struct io_msg, tw);
+	struct io_kiocb *req = cmd_to_io_kiocb(msg);
+	int ret = -EOWNERDEAD;
+
+	if (!(current->flags & PF_EXITING))
+		ret = io_msg_install_complete(req, IO_URING_F_UNLOCKED);
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_queue_tw_complete(req, ret);
+}
+
+static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_ring_ctx *target_ctx = req->file->private_data;
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct file *src_file = msg->src_file;
+
+	if (msg->len)
+		return -EINVAL;
+	if (target_ctx == ctx)
+		return -EINVAL;
+	if (target_ctx->flags & IORING_SETUP_R_DISABLED)
+		return -EBADFD;
+	if (!src_file) {
+		src_file = io_msg_grab_file(req, issue_flags);
+		if (!src_file)
+			return -EBADF;
+		msg->src_file = src_file;
+		req->flags |= REQ_F_NEED_CLEANUP;
+	}
+
+	if (io_msg_need_remote(target_ctx))
+		return io_msg_exec_remote(req, io_msg_tw_fd_complete);
+	return io_msg_install_complete(req, issue_flags);
+}
+
+int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+
+	if (unlikely(sqe->buf_index || sqe->personality))
+		return -EINVAL;
+
+	msg->src_file = NULL;
+	msg->user_data = READ_ONCE(sqe->off);
+	msg->len = READ_ONCE(sqe->len);
+	msg->cmd = READ_ONCE(sqe->addr);
+	msg->src_fd = READ_ONCE(sqe->addr3);
+	msg->dst_fd = READ_ONCE(sqe->file_index);
+	msg->flags = READ_ONCE(sqe->msg_ring_flags);
+	if (msg->flags & ~IORING_MSG_RING_MASK)
+		return -EINVAL;
+
+	return 0;
+}
+
+int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+	int ret;
+
+	ret = -EBADFD;
+	if (!io_is_uring_fops(req->file))
+		goto done;
+
+	switch (msg->cmd) {
+	case IORING_MSG_DATA:
+		ret = io_msg_ring_data(req, issue_flags);
+		break;
+	case IORING_MSG_SEND_FD:
+		ret = io_msg_send_fd(req, issue_flags);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+done:
+	if (ret < 0) {
+		if (ret == -EAGAIN || ret == IOU_ISSUE_SKIP_COMPLETE)
+			return ret;
+		req_set_fail(req);
+	}
+	io_req_set_res(req, ret, 0);
+	return IOU_OK;
+}