net.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/un.h>
#include <linux/compat.h>
#include <net/compat.h>
#include <linux/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "filetable.h"
#include "io_uring.h"
#include "kbuf.h"
#include "alloc_cache.h"
#include "net.h"
#include "notif.h"
#include "rsrc.h"
#include "zcrx.h"

struct io_shutdown {
	struct file			*file;
	int				how;
};

struct io_accept {
	struct file			*file;
	struct sockaddr __user		*addr;
	int __user			*addr_len;
	int				flags;
	int				iou_flags;
	u32				file_slot;
	unsigned long			nofile;
};

struct io_socket {
	struct file			*file;
	int				domain;
	int				type;
	int				protocol;
	int				flags;
	u32				file_slot;
	unsigned long			nofile;
};

struct io_connect {
	struct file			*file;
	struct sockaddr __user		*addr;
	int				addr_len;
	bool				in_progress;
	bool				seen_econnaborted;
};

struct io_bind {
	struct file			*file;
	int				addr_len;
};

struct io_listen {
	struct file			*file;
	int				backlog;
};

struct io_sr_msg {
	struct file			*file;
	union {
		struct compat_msghdr __user	*umsg_compat;
		struct user_msghdr __user	*umsg;
		void __user			*buf;
	};
	int				len;
	unsigned			done_io;
	unsigned			msg_flags;
	unsigned			nr_multishot_loops;
	u16				flags;
	/* initialised and used only by !msg send variants */
	u16				buf_group;
	/* per-invocation mshot limit */
	unsigned			mshot_len;
	/* overall mshot byte limit */
	unsigned			mshot_total_len;
	void __user			*msg_control;
	/* used only for send zerocopy */
	struct io_kiocb 		*notif;
};

/*
 * The UAPI flags are the lower 8 bits, as that's all sqe->ioprio will hold
 * anyway. Use the upper 8 bits for internal uses.
 */
enum sr_retry_flags {
	IORING_RECV_RETRY	= (1U << 15),
	IORING_RECV_PARTIAL_MAP	= (1U << 14),
	IORING_RECV_MSHOT_CAP	= (1U << 13),
	IORING_RECV_MSHOT_LIM	= (1U << 12),
	IORING_RECV_MSHOT_DONE	= (1U << 11),

	IORING_RECV_RETRY_CLEAR	= IORING_RECV_RETRY | IORING_RECV_PARTIAL_MAP,
	IORING_RECV_NO_RETRY	= IORING_RECV_RETRY | IORING_RECV_PARTIAL_MAP |
				  IORING_RECV_MSHOT_CAP | IORING_RECV_MSHOT_DONE,
};

/*
 * Number of times we'll try and do receives if there's more data. If we
 * exceed this limit, then add us to the back of the queue and retry from
 * there. This helps fairness between flooding clients.
 */
#define MULTISHOT_MAX_RETRY	32

struct io_recvzc {
	struct file			*file;
	u16				flags;
	u32				len;
	struct io_zcrx_ifq		*ifq;
};

static int io_sg_from_iter_iovec(struct sk_buff *skb,
				 struct iov_iter *from, size_t length);
static int io_sg_from_iter(struct sk_buff *skb,
			   struct iov_iter *from, size_t length);

int io_shutdown_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_shutdown *shutdown = io_kiocb_to_cmd(req, struct io_shutdown);

	if (unlikely(sqe->off || sqe->addr || sqe->rw_flags ||
		     sqe->buf_index || sqe->splice_fd_in))
		return -EINVAL;

	shutdown->how = READ_ONCE(sqe->len);
	req->flags |= REQ_F_FORCE_ASYNC;
	return 0;
}

int io_shutdown(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_shutdown *shutdown = io_kiocb_to_cmd(req, struct io_shutdown);
	struct socket *sock;
	int ret;

	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);

	sock = sock_from_file(req->file);
	if (unlikely(!sock))
		return -ENOTSOCK;

	ret = __sys_shutdown_sock(sock, shutdown->how);
	io_req_set_res(req, ret, 0);
	return IOU_COMPLETE;
}

static bool io_net_retry(struct socket *sock, int flags)
{
	if (!(flags & MSG_WAITALL))
		return false;
	return sock->type == SOCK_STREAM || sock->type == SOCK_SEQPACKET;
}

static void io_netmsg_iovec_free(struct io_async_msghdr *kmsg)
{
	if (kmsg->vec.iovec)
		io_vec_free(&kmsg->vec);
}

static void io_netmsg_recycle(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_async_msghdr *hdr = req->async_data;

	/* can't recycle, ensure we free the iovec if we have one */
	if (unlikely(issue_flags & IO_URING_F_UNLOCKED)) {
		io_netmsg_iovec_free(hdr);
		return;
	}

	/* Let normal cleanup path reap it if we fail adding to the cache */
	io_alloc_cache_vec_kasan(&hdr->vec);
	if (hdr->vec.nr > IO_VEC_CACHE_SOFT_CAP)
		io_vec_free(&hdr->vec);

	if (io_alloc_cache_put(&req->ctx->netmsg_cache, hdr))
		io_req_async_data_clear(req, REQ_F_NEED_CLEANUP);
}

static struct io_async_msghdr *io_msg_alloc_async(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct io_async_msghdr *hdr;

	hdr = io_uring_alloc_async_data(&ctx->netmsg_cache, req);
	if (!hdr)
		return NULL;

	/* If the async data was cached, we might have an iov cached inside. */
	if (hdr->vec.iovec)
		req->flags |= REQ_F_NEED_CLEANUP;
	return hdr;
}

static inline void io_mshot_prep_retry(struct io_kiocb *req,
				       struct io_async_msghdr *kmsg)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);

	req->flags &= ~REQ_F_BL_EMPTY;
	sr->done_io = 0;
	sr->flags &= ~IORING_RECV_RETRY_CLEAR;
	sr->len = sr->mshot_len;
}

static int io_net_import_vec(struct io_kiocb *req, struct io_async_msghdr *iomsg,
			     const struct iovec __user *uiov, unsigned uvec_seg,
			     int ddir)
{
	struct iovec *iov;
	int ret, nr_segs;

	if (iomsg->vec.iovec) {
		nr_segs = iomsg->vec.nr;
		iov = iomsg->vec.iovec;
	} else {
		nr_segs = 1;
		iov = &iomsg->fast_iov;
	}

	ret = __import_iovec(ddir, uiov, uvec_seg, nr_segs, &iov,
			     &iomsg->msg.msg_iter, io_is_compat(req->ctx));
	if (unlikely(ret < 0))
		return ret;

	if (iov) {
		req->flags |= REQ_F_NEED_CLEANUP;
		io_vec_reset_iovec(&iomsg->vec, iov, iomsg->msg.msg_iter.nr_segs);
	}
	return 0;
}

static int io_copy_msghdr_from_user(struct user_msghdr *msg,
				    struct user_msghdr __user *umsg)
{
	if (!user_access_begin(umsg, sizeof(*umsg)))
		return -EFAULT;
	unsafe_get_user(msg->msg_name, &umsg->msg_name, ua_end);
	unsafe_get_user(msg->msg_namelen, &umsg->msg_namelen, ua_end);
	unsafe_get_user(msg->msg_iov, &umsg->msg_iov, ua_end);
	unsafe_get_user(msg->msg_iovlen, &umsg->msg_iovlen, ua_end);
	unsafe_get_user(msg->msg_control, &umsg->msg_control, ua_end);
	unsafe_get_user(msg->msg_controllen, &umsg->msg_controllen, ua_end);
	user_access_end();
	return 0;
ua_end:
	user_access_end();
	return -EFAULT;
}

static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg,
			   struct user_msghdr *msg,
			   struct sockaddr __user **save_addr)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	int ret;

	iomsg->msg.msg_name = &iomsg->addr;
	iomsg->msg.msg_iter.nr_segs = 0;

	if (io_is_compat(req->ctx)) {
		struct compat_msghdr cmsg;

		if (copy_from_user(&cmsg, sr->umsg_compat, sizeof(cmsg)))
			return -EFAULT;

		ret = __get_compat_msghdr(&iomsg->msg, &cmsg, save_addr);
		if (ret)
			return ret;

		memset(msg, 0, sizeof(*msg));
		msg->msg_namelen = cmsg.msg_namelen;
		msg->msg_controllen = cmsg.msg_controllen;
		msg->msg_iov = compat_ptr(cmsg.msg_iov);
		msg->msg_iovlen = cmsg.msg_iovlen;
	} else {
		ret = io_copy_msghdr_from_user(msg, sr->umsg);
		if (unlikely(ret))
			return ret;

		msg->msg_flags = 0;

		ret = __copy_msghdr(&iomsg->msg, msg, save_addr);
		if (ret)
			return ret;
	}

	if (req->flags & REQ_F_BUFFER_SELECT) {
		if (msg->msg_iovlen == 0) {
			sr->len = 0;
		} else if (msg->msg_iovlen > 1) {
			return -EINVAL;
		} else {
			struct iovec fast_iov, *iov;

			iov = iovec_from_user(msg->msg_iov, 1, 1, &fast_iov,
					      io_is_compat(req->ctx));
			if (IS_ERR(iov))
				return PTR_ERR(iov);
			sr->len = iov->iov_len;
		}
	}
	return 0;
}

void io_sendmsg_recvmsg_cleanup(struct io_kiocb *req)
{
	struct io_async_msghdr *io = req->async_data;

	io_netmsg_iovec_free(io);
}

static int io_send_setup(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	struct io_async_msghdr *kmsg = req->async_data;
	void __user *addr;
	u16 addr_len;
	int ret;

	sr->buf = u64_to_user_ptr(READ_ONCE(sqe->addr));

	if (READ_ONCE(sqe->__pad3[0]))
		return -EINVAL;

	kmsg->msg.msg_name = NULL;
	kmsg->msg.msg_namelen = 0;
	kmsg->msg.msg_control = NULL;
	kmsg->msg.msg_controllen = 0;
	kmsg->msg.msg_ubuf = NULL;

	addr = u64_to_user_ptr(READ_ONCE(sqe->addr2));
	addr_len = READ_ONCE(sqe->addr_len);
	if (addr) {
		ret = move_addr_to_kernel(addr, addr_len, &kmsg->addr);
		if (unlikely(ret < 0))
			return ret;
		kmsg->msg.msg_name = &kmsg->addr;
		kmsg->msg.msg_namelen = addr_len;
	}
	if (sr->flags & IORING_RECVSEND_FIXED_BUF) {
		if (!(sr->flags & IORING_SEND_VECTORIZED)) {
			req->flags |= REQ_F_IMPORT_BUFFER;
			return 0;
		}

		kmsg->msg.msg_iter.nr_segs = sr->len;
		return io_prep_reg_iovec(req, &kmsg->vec, sr->buf, sr->len);
	}
	if (req->flags & REQ_F_BUFFER_SELECT)
		return 0;

	if (sr->flags & IORING_SEND_VECTORIZED)
		return io_net_import_vec(req, kmsg, sr->buf, sr->len, ITER_SOURCE);

	return import_ubuf(ITER_SOURCE, sr->buf, sr->len, &kmsg->msg.msg_iter);
}

static int io_sendmsg_setup(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	struct io_async_msghdr *kmsg = req->async_data;
	struct user_msghdr msg;
	int ret;

	sr->flags |= IORING_SEND_VECTORIZED;
	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
	ret = io_msg_copy_hdr(req, kmsg, &msg, NULL);
	if (unlikely(ret))
		return ret;
	/* save msg_control as sys_sendmsg() overwrites it */
	sr->msg_control = kmsg->msg.msg_control_user;

	if (sr->flags & IORING_RECVSEND_FIXED_BUF) {
		kmsg->msg.msg_iter.nr_segs = msg.msg_iovlen;
		return io_prep_reg_iovec(req, &kmsg->vec, msg.msg_iov,
					 msg.msg_iovlen);
	}
	if (req->flags & REQ_F_BUFFER_SELECT)
		return 0;
	return io_net_import_vec(req, kmsg, msg.msg_iov, msg.msg_iovlen, ITER_SOURCE);
}

#define SENDMSG_FLAGS (IORING_RECVSEND_POLL_FIRST | IORING_RECVSEND_BUNDLE | \
			IORING_SEND_VECTORIZED | IORING_RECVSEND_FIXED_BUF)

int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);

	sr->done_io = 0;
	sr->len = READ_ONCE(sqe->len);
	if (unlikely(sr->len < 0))
		return -EINVAL;
	sr->flags = READ_ONCE(sqe->ioprio);
	if (sr->flags & ~SENDMSG_FLAGS)
		return -EINVAL;
	if (sr->flags & IORING_RECVSEND_FIXED_BUF) {
		/* registered buffer send only supported for plain IORING_OP_SEND */
		if (req->opcode != IORING_OP_SEND ||
		    (req->flags & REQ_F_BUFFER_SELECT) ||
		    (sr->flags & (IORING_RECVSEND_BUNDLE|IORING_SEND_VECTORIZED)))
			return -EINVAL;
		req->buf_index = READ_ONCE(sqe->buf_index);
	}
	sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
	if (sr->msg_flags & MSG_DONTWAIT)
		req->flags |= REQ_F_NOWAIT;
	if (req->flags & REQ_F_BUFFER_SELECT)
		sr->buf_group = req->buf_index;
	sr->mshot_total_len = sr->mshot_len = 0;
	if (sr->flags & IORING_RECVSEND_BUNDLE) {
		if (req->opcode == IORING_OP_SENDMSG)
			return -EINVAL;
		sr->msg_flags |= MSG_WAITALL;
		req->flags |= REQ_F_MULTISHOT;
	}

	if (io_is_compat(req->ctx))
		sr->msg_flags |= MSG_CMSG_COMPAT;

	if (unlikely(!io_msg_alloc_async(req)))
		return -ENOMEM;
	if (req->opcode != IORING_OP_SENDMSG)
		return io_send_setup(req, sqe);
	if (unlikely(sqe->addr2 || sqe->file_index))
		return -EINVAL;
	return io_sendmsg_setup(req, sqe);
}

static void io_req_msg_cleanup(struct io_kiocb *req,
			       unsigned int issue_flags)
{
	io_netmsg_recycle(req, issue_flags);
}

/*
 * For bundle completions, we need to figure out how many segments we consumed.
 * A bundle could be using a single ITER_UBUF if that's all we mapped, or it
 * could be using an ITER_IOVEC. If the latter, then if we consumed all of
 * the segments, then it's a trivial questiont o answer. If we have residual
 * data in the iter, then loop the segments to figure out how much we
 * transferred.
 */
static int io_bundle_nbufs(struct io_async_msghdr *kmsg, int ret)
{
	struct iovec *iov;
	int nbufs;

	/* no data is always zero segments, and a ubuf is always 1 segment */
	if (ret <= 0)
		return 0;
	if (iter_is_ubuf(&kmsg->msg.msg_iter))
		return 1;

	iov = kmsg->vec.iovec;
	if (!iov)
		iov = &kmsg->fast_iov;

	/* if all data was transferred, it's basic pointer math */
	if (!iov_iter_count(&kmsg->msg.msg_iter))
		return iter_iov(&kmsg->msg.msg_iter) - iov;

	/* short transfer, count segments */
	nbufs = 0;
	do {
		int this_len = min_t(int, iov[nbufs].iov_len, ret);

		nbufs++;
		ret -= this_len;
	} while (ret);

	return nbufs;
}

static int io_net_kbuf_recyle(struct io_kiocb *req, struct io_buffer_list *bl,
			      struct io_async_msghdr *kmsg, int len)
{
	req->flags |= REQ_F_BL_NO_RECYCLE;
	if (req->flags & REQ_F_BUFFERS_COMMIT)
		io_kbuf_commit(req, bl, len, io_bundle_nbufs(kmsg, len));
	return IOU_RETRY;
}

static inline bool io_send_finish(struct io_kiocb *req,
				  struct io_async_msghdr *kmsg,
				  struct io_br_sel *sel)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	bool bundle_finished = sel->val <= 0;
	unsigned int cflags;

	if (!(sr->flags & IORING_RECVSEND_BUNDLE)) {
		cflags = io_put_kbuf(req, sel->val, sel->buf_list);
		goto finish;
	}

	cflags = io_put_kbufs(req, sel->val, sel->buf_list, io_bundle_nbufs(kmsg, sel->val));

	/*
	 * Don't start new bundles if the buffer list is empty, or if the
	 * current operation needed to go through polling to complete.
	 */
	if (bundle_finished || req->flags & (REQ_F_BL_EMPTY | REQ_F_POLLED))
		goto finish;

	/*
	 * Fill CQE for this receive and see if we should keep trying to
	 * receive from this socket.
	 */
	if (io_req_post_cqe(req, sel->val, cflags | IORING_CQE_F_MORE)) {
		io_mshot_prep_retry(req, kmsg);
		return false;
	}

	/* Otherwise stop bundle and use the current result. */
finish:
	io_req_set_res(req, sel->val, cflags);
	sel->val = IOU_COMPLETE;
	return true;
}

int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	struct io_async_msghdr *kmsg = req->async_data;
	struct socket *sock;
	unsigned flags;
	int min_ret = 0;
	int ret;

	sock = sock_from_file(req->file);
	if (unlikely(!sock))
		return -ENOTSOCK;

	if (!(req->flags & REQ_F_POLLED) &&
	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
		return -EAGAIN;

	flags = sr->msg_flags;
	if (issue_flags & IO_URING_F_NONBLOCK)
		flags |= MSG_DONTWAIT;
	if (flags & MSG_WAITALL)
		min_ret = iov_iter_count(&kmsg->msg.msg_iter);

	kmsg->msg.msg_control_user = sr->msg_control;

	ret = __sys_sendmsg_sock(sock, &kmsg->msg, flags);

	if (ret < min_ret) {
		if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
			return -EAGAIN;
		if (ret > 0 && io_net_retry(sock, flags)) {
			kmsg->msg.msg_controllen = 0;
			kmsg->msg.msg_control = NULL;
			sr->done_io += ret;
			return -EAGAIN;
		}
		if (ret == -ERESTARTSYS)
			ret = -EINTR;
		req_set_fail(req);
	}
	io_req_msg_cleanup(req, issue_flags);
	if (ret >= 0)
		ret += sr->done_io;
	else if (sr->done_io)
		ret = sr->done_io;
	io_req_set_res(req, ret, 0);
	return IOU_COMPLETE;
}

static int io_send_select_buffer(struct io_kiocb *req, unsigned int issue_flags,
				 struct io_br_sel *sel, struct io_async_msghdr *kmsg)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	struct buf_sel_arg arg = {
		.iovs = &kmsg->fast_iov,
		.max_len = min_not_zero(sr->len, INT_MAX),
		.nr_iovs = 1,
		.buf_group = sr->buf_group,
	};
	int ret;

	if (kmsg->vec.iovec) {
		arg.nr_iovs = kmsg->vec.nr;
		arg.iovs = kmsg->vec.iovec;
		arg.mode = KBUF_MODE_FREE;
	}

	if (!(sr->flags & IORING_RECVSEND_BUNDLE))
		arg.nr_iovs = 1;
	else
		arg.mode |= KBUF_MODE_EXPAND;

	ret = io_buffers_select(req, &arg, sel, issue_flags);
	if (unlikely(ret < 0))
		return ret;

	if (arg.iovs != &kmsg->fast_iov && arg.iovs != kmsg->vec.iovec) {
		kmsg->vec.nr = ret;
		kmsg->vec.iovec = arg.iovs;
		req->flags |= REQ_F_NEED_CLEANUP;
	}
	sr->len = arg.out_len;

	if (ret == 1) {
		sr->buf = arg.iovs[0].iov_base;
		ret = import_ubuf(ITER_SOURCE, sr->buf, sr->len,
					&kmsg->msg.msg_iter);
		if (unlikely(ret))
			return ret;
	} else {
		iov_iter_init(&kmsg->msg.msg_iter, ITER_SOURCE,
				arg.iovs, ret, arg.out_len);
	}

	return 0;
}

int io_send(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	struct io_async_msghdr *kmsg = req->async_data;
	struct io_br_sel sel = { };
	struct socket *sock;
	unsigned flags;
	int min_ret = 0;
	int ret;

	sock = sock_from_file(req->file);
	if (unlikely(!sock))
		return -ENOTSOCK;

	if (!(req->flags & REQ_F_POLLED) &&
	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
		return -EAGAIN;

	if (req->flags & REQ_F_IMPORT_BUFFER) {
		ret = io_import_reg_buf(req, &kmsg->msg.msg_iter,
					(u64)(uintptr_t)sr->buf, sr->len,
					ITER_SOURCE, issue_flags);
		if (unlikely(ret))
			return ret;
		req->flags &= ~REQ_F_IMPORT_BUFFER;
	}

	flags = sr->msg_flags;
	if (issue_flags & IO_URING_F_NONBLOCK)
		flags |= MSG_DONTWAIT;

retry_bundle:
	sel.buf_list = NULL;
	if (io_do_buffer_select(req)) {
		ret = io_send_select_buffer(req, issue_flags, &sel, kmsg);
		if (ret)
			return ret;
	}

	/*
	 * If MSG_WAITALL is set, or this is a bundle send, then we need
	 * the full amount. If just bundle is set, if we do a short send
	 * then we complete the bundle sequence rather than continue on.
	 */
	if (flags & MSG_WAITALL || sr->flags & IORING_RECVSEND_BUNDLE)
		min_ret = iov_iter_count(&kmsg->msg.msg_iter);

	flags &= ~MSG_INTERNAL_SENDMSG_FLAGS;
	kmsg->msg.msg_flags = flags;
	ret = sock_sendmsg(sock, &kmsg->msg);
	if (ret < min_ret) {
		if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
			return -EAGAIN;

		if (ret > 0 && io_net_retry(sock, flags)) {
			sr->len -= ret;
			sr->buf += ret;
			sr->done_io += ret;
			return io_net_kbuf_recyle(req, sel.buf_list, kmsg, ret);
		}
		if (ret == -ERESTARTSYS)
			ret = -EINTR;
		req_set_fail(req);
	}
	if (ret >= 0)
		ret += sr->done_io;
	else if (sr->done_io)
		ret = sr->done_io;

	sel.val = ret;
	if (!io_send_finish(req, kmsg, &sel))
		goto retry_bundle;

	io_req_msg_cleanup(req, issue_flags);
	return sel.val;
}

static int io_recvmsg_mshot_prep(struct io_kiocb *req,
				 struct io_async_msghdr *iomsg,
				 int namelen, size_t controllen)
{
	if ((req->flags & (REQ_F_APOLL_MULTISHOT|REQ_F_BUFFER_SELECT)) ==
			  (REQ_F_APOLL_MULTISHOT|REQ_F_BUFFER_SELECT)) {
		int hdr;

		if (unlikely(namelen < 0))
			return -EOVERFLOW;
		if (check_add_overflow(sizeof(struct io_uring_recvmsg_out),
					namelen, &hdr))
			return -EOVERFLOW;
		if (check_add_overflow(hdr, controllen, &hdr))
			return -EOVERFLOW;

		iomsg->namelen = namelen;
		iomsg->controllen = controllen;
		return 0;
	}

	return 0;
}

static int io_recvmsg_copy_hdr(struct io_kiocb *req,
			       struct io_async_msghdr *iomsg)
{
	struct user_msghdr msg;
	int ret;

	ret = io_msg_copy_hdr(req, iomsg, &msg, &iomsg->uaddr);
	if (unlikely(ret))
		return ret;

	if (!(req->flags & REQ_F_BUFFER_SELECT)) {
		ret = io_net_import_vec(req, iomsg, msg.msg_iov, msg.msg_iovlen,
					ITER_DEST);
		if (unlikely(ret))
			return ret;
	}
	return io_recvmsg_mshot_prep(req, iomsg, msg.msg_namelen,
					msg.msg_controllen);
}

static int io_recvmsg_prep_setup(struct io_kiocb *req)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	struct io_async_msghdr *kmsg;

	kmsg = io_msg_alloc_async(req);
	if (unlikely(!kmsg))
		return -ENOMEM;

	if (req->opcode == IORING_OP_RECV) {
		kmsg->msg.msg_name = NULL;
		kmsg->msg.msg_namelen = 0;
		kmsg->msg.msg_inq = 0;
		kmsg->msg.msg_control = NULL;
		kmsg->msg.msg_get_inq = 1;
		kmsg->msg.msg_controllen = 0;
		kmsg->msg.msg_ubuf = NULL;

		if (req->flags & REQ_F_BUFFER_SELECT)
			return 0;
		if (sr->flags & IORING_RECVSEND_FIXED_BUF) {
			req->flags |= REQ_F_IMPORT_BUFFER;
			return 0;
		}
		return import_ubuf(ITER_DEST, sr->buf, sr->len,
				   &kmsg->msg.msg_iter);
	}

	return io_recvmsg_copy_hdr(req, kmsg);
}

#define RECVMSG_FLAGS (IORING_RECVSEND_POLL_FIRST | IORING_RECV_MULTISHOT | \
			IORING_RECVSEND_BUNDLE | IORING_RECVSEND_FIXED_BUF)

int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);

	sr->done_io = 0;

	if (unlikely(sqe->addr2))
		return -EINVAL;

	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
	sr->len = READ_ONCE(sqe->len);
	if (unlikely(sr->len < 0))
		return -EINVAL;
	sr->flags = READ_ONCE(sqe->ioprio);
	if (sr->flags & ~RECVMSG_FLAGS)
		return -EINVAL;
	if (sr->flags & IORING_RECVSEND_FIXED_BUF) {
		/* registered buffer recv only for plain IORING_OP_RECV */
		if (req->opcode != IORING_OP_RECV ||
		    (req->flags & REQ_F_BUFFER_SELECT) ||
		    (sr->flags & (IORING_RECV_MULTISHOT | IORING_RECVSEND_BUNDLE)))
			return -EINVAL;
		req->buf_index = READ_ONCE(sqe->buf_index);
	}
	sr->msg_flags = READ_ONCE(sqe->msg_flags);
	if (sr->msg_flags & MSG_DONTWAIT)
		req->flags |= REQ_F_NOWAIT;
	if (sr->msg_flags & MSG_ERRQUEUE)
		req->flags |= REQ_F_CLEAR_POLLIN;
	if (req->flags & REQ_F_BUFFER_SELECT)
		sr->buf_group = req->buf_index;
	sr->mshot_total_len = sr->mshot_len = 0;
	if (sr->flags & IORING_RECV_MULTISHOT) {
		if (!(req->flags & REQ_F_BUFFER_SELECT))
			return -EINVAL;
		if (sr->msg_flags & MSG_WAITALL)
			return -EINVAL;
		if (req->opcode == IORING_OP_RECV) {
			sr->mshot_len = sr->len;
			sr->mshot_total_len = READ_ONCE(sqe->optlen);
			if (sr->mshot_total_len)
				sr->flags |= IORING_RECV_MSHOT_LIM;
		} else if (sqe->optlen) {
			return -EINVAL;
		}
		req->flags |= REQ_F_APOLL_MULTISHOT;
	} else if (sqe->optlen) {
		return -EINVAL;
	}

	if (sr->flags & IORING_RECVSEND_BUNDLE) {
		if (req->opcode == IORING_OP_RECVMSG)
			return -EINVAL;
	}

	if (io_is_compat(req->ctx))
		sr->msg_flags |= MSG_CMSG_COMPAT;

	sr->nr_multishot_loops = 0;
	return io_recvmsg_prep_setup(req);
}

/* bits to clear in old and inherit in new cflags on bundle retry */
#define CQE_F_MASK	(IORING_CQE_F_SOCK_NONEMPTY|IORING_CQE_F_MORE|\
			 IORING_CQE_F_BUF_MORE)

/*
 * Finishes io_recv and io_recvmsg.
 *
 * Returns true if it is actually finished, or false if it should run
 * again (for multishot).
 */
static inline bool io_recv_finish(struct io_kiocb *req,
				  struct io_async_msghdr *kmsg,
				  struct io_br_sel *sel, bool mshot_finished,
				  unsigned issue_flags, int consumed)
{
	struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg);
	unsigned int cflags = 0;

	if (kmsg->msg.msg_inq > 0)
		cflags |= IORING_CQE_F_SOCK_NONEMPTY;

	if (sel->val > 0 && sr->flags & IORING_RECV_MSHOT_LIM) {
		/*
		 * If sr->len hits zero, the limit has been reached. Mark
		 * mshot as finished, and flag MSHOT_DONE as well to prevent
		 * a potential bundle from being retried.
		 */
		sr->mshot_total_len -= min_t(int, sel->val, sr->mshot_total_len);
		if (!sr->mshot_total_len) {
			sr->flags |= IORING_RECV_MSHOT_DONE;
			mshot_finished = true;
		}
	}

	if (sr->flags & IORING_RECVSEND_BUNDLE) {
		size_t this_ret = sel->val - sr->done_io;

		cflags |= io_put_kbufs(req, consumed, sel->buf_list, io_bundle_nbufs(kmsg, consumed));
		if (sr->flags & IORING_RECV_RETRY)
			cflags = req->cqe.flags | (cflags & CQE_F_MASK);
		if (sr->mshot_len && sel->val >= sr->mshot_len)
			sr->flags |= IORING_RECV_MSHOT_CAP;
		/* bundle with no more immediate buffers, we're done */
		if (req->flags & REQ_F_BL_EMPTY)
			goto finish;
		/*
		 * If more is available AND it was a full transfer, retry and
		 * append to this one
		 */
		if (!(sr->flags & IORING_RECV_NO_RETRY) &&
		    kmsg->msg.msg_inq > 1 && this_ret > 0 &&
		    !iov_iter_count(&kmsg->msg.msg_iter)) {
			req->cqe.flags = cflags & ~CQE_F_MASK;
			sr->len = kmsg->msg.msg_inq;
			sr->done_io += this_ret;
			sr->flags |= IORING_RECV_RETRY;
			return false;
		}
	} else {
		cflags |= io_put_kbuf(req, consumed, sel->buf_list);
	}

	/*
	 * Fill CQE for this receive and see if we should keep trying to
	 * receive from this socket.
	 */
	if ((req->flags & REQ_F_APOLL_MULTISHOT) && !mshot_finished &&
	    io_req_post_cqe(req, sel->val, cflags | IORING_CQE_F_MORE)) {
		sel->val = IOU_RETRY;
		io_mshot_prep_retry(req, kmsg);
		/* Known not-empty or unknown state, retry */
		if (cflags & IORING_CQE_F_SOCK_NONEMPTY || kmsg->msg.msg_inq < 0) {
			if (sr->nr_multishot_loops++ < MULTISHOT_MAX_RETRY &&
			    !(sr->flags & IORING_RECV_MSHOT_CAP)) {
				return false;
			}
			/* mshot retries exceeded, force a requeue */
			sr->nr_multishot_loops = 0;
			sr->flags &= ~IORING_RECV_MSHOT_CAP;
			if (issue_flags & IO_URING_F_MULTISHOT)
				sel->val = IOU_REQUEUE;
		}
		return true;
	}

	/* Finish the request / stop multishot. */
finish:
	io_req_set_res(req, sel->val, cflags);
	sel->val = IOU_COMPLETE;
	io_req_msg_cleanup(req, issue_flags);
	return true;
}

static int io_recvmsg_prep_multishot(struct io_async_msghdr *kmsg,
				     struct io_sr_msg *sr, void __user **buf,
				     size_t *len)
{
	unsigned long ubuf = (unsigned long) *buf;
	unsigned long hdr;

	hdr = sizeof(struct io_uring_recvmsg_out) + kmsg->namelen +
		kmsg->controllen;
	if (*len < hdr)
		return -EFAULT;

	if (kmsg->controllen) {
		unsigned long control = ubuf + hdr - kmsg->controllen;

		kmsg->msg.msg_control_user = (void __user *) control;
		kmsg->msg.msg_controllen = kmsg->controllen;
	}

	sr->buf = *buf; /* stash for later copy */
	*buf = (void __user *) (ubuf + hdr);
	kmsg->payloadlen = *len = *len - hdr;
	return 0;
}

struct io_recvmsg_multishot_hdr {
	struct io_uring_recvmsg_out msg;
	struct sockaddr_storage addr;
};

static int io_recvmsg_multishot(struct socket *sock, struct io_sr_msg *io,
				struct io_async_msghdr *kmsg,
				unsigned int flags, bool *finished)
{
	int err;
	int copy_len;
	struct io_recvmsg_multishot_hdr hdr;

	if (kmsg->namelen)
		kmsg->msg.msg_name = &hdr.addr;
	kmsg->msg.msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
	kmsg->msg.msg_namelen = 0;

	if (sock->file->f_flags & O_NONBLOCK)
		flags |= MSG_DONTWAIT;

	err = sock_recvmsg(sock, &kmsg->msg, flags);
	*finished = err <= 0;
	if (err < 0)
		return err;

	hdr.msg = (struct io_uring_recvmsg_out) {
		.controllen = kmsg->controllen - kmsg->msg.msg_controllen,
		.flags = kmsg->msg.msg_flags & ~MSG_CMSG_COMPAT
	};

	hdr.msg.payloadlen = err;
	if (err > kmsg->payloadlen)
		err = kmsg->payloadlen;

	copy_len = sizeof(struct io_uring_recvmsg_out);
	if (kmsg->msg.msg_namelen > kmsg->namelen)
		copy_len += kmsg->namelen;
	else
		copy_len += kmsg->msg.msg_namelen;