// 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_lock_external_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)
{
        return target_ctx->task_complete;
}

static void io_msg_tw_complete(struct io_tw_req tw_req, io_tw_token_t tw)
{
        struct io_kiocb *req = tw_req.req;
        struct io_ring_ctx *ctx = req->ctx;

        io_add_aux_cqe(ctx, req->cqe.user_data, req->cqe.res, req->cqe.flags);
        kfree_rcu(req, rcu_head);
        percpu_ref_put(&ctx->refs);
}

static void io_msg_remote_post(struct io_ring_ctx *ctx, struct io_kiocb *req,
                              int res, u32 cflags, u64 user_data)
{
        req->opcode = IORING_OP_NOP;
        req->cqe.user_data = user_data;
        io_req_set_res(req, res, cflags);
        percpu_ref_get(&ctx->refs);
        req->ctx = ctx;
        req->tctx = NULL;
        req->io_task_work.func = io_msg_tw_complete;
        io_req_task_work_add_remote(req, IOU_F_TWQ_LAZY_WAKE);
}

static int io_msg_data_remote(struct io_ring_ctx *target_ctx,
                              struct io_msg *msg)
{
        struct io_kiocb *target;
        u32 flags = 0;

        target = kmem_cache_alloc(req_cachep, GFP_KERNEL | __GFP_NOWARN | __GFP_ZERO)  ;
        if (unlikely(!target))
                return -ENOMEM;

        if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
                flags = msg->cqe_flags;

        io_msg_remote_post(target_ctx, target, msg->len, flags, msg->user_data);
        return 0;
}

static int __io_msg_ring_data(struct io_ring_ctx *target_ctx,
                              struct io_msg *msg, unsigned int issue_flags)
{
        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;
        /*
         * Keep IORING_SETUP_R_DISABLED check before submitter_task load
         * in io_msg_data_remote() -> io_req_task_work_add_remote()
         */
        if (smp_load_acquire(&target_ctx->flags) & IORING_SETUP_R_DISABLED)
                return -EBADFD;

        if (io_msg_need_remote(target_ctx))
                return io_msg_data_remote(target_ctx, msg);

        if (msg->flags & IORING_MSG_RING_FLAGS_PASS)
                flags = msg->cqe_flags;

        ret = -EOVERFLOW;
        if (target_ctx->flags & IORING_SETUP_IOPOLL) {
                if (unlikely(io_lock_external_ctx(target_ctx, issue_flags)))
                        return -EAGAIN;
        }
        if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, flags))
                ret = 0;
        if (target_ctx->flags & IORING_SETUP_IOPOLL)
                io_double_unlock_ctx(target_ctx);
        return 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);

        return __io_msg_ring_data(target_ctx, msg, issue_flags);
}

static int 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 io_rsrc_node *node;
        int ret = -EBADF;

        io_ring_submit_lock(ctx, issue_flags);
        node = io_rsrc_node_lookup(&ctx->file_table.data, msg->src_fd);
        if (node) {
                msg->src_file = io_slot_file(node);
                if (msg->src_file)
                        get_file(msg->src_file);
                req->flags |= REQ_F_NEED_CLEANUP;
                ret = 0;
        }
        io_ring_submit_unlock(ctx, issue_flags);
        return ret;
}

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_lock_external_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_fd_remote(struct io_kiocb *req)
{
        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 = ctx->submitter_task;

        init_task_work(&msg->tw, io_msg_tw_fd_complete);
        if (task_work_add(task, &msg->tw, TWA_SIGNAL))
                return -EOWNERDEAD;

        return IOU_ISSUE_SKIP_COMPLETE;
}

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;

        if (msg->len)
                return -EINVAL;
        if (target_ctx == ctx)
                return -EINVAL;
        /*
         * Keep IORING_SETUP_R_DISABLED check before submitter_task load
         * in io_msg_fd_remote()
         */
        if (smp_load_acquire(&target_ctx->flags) & IORING_SETUP_R_DISABLED)
                return -EBADFD;
        if (!msg->src_file) {
                int ret = io_msg_grab_file(req, issue_flags);
                if (unlikely(ret))
                        return ret;
        }

        if (io_msg_need_remote(target_ctx))
                return io_msg_fd_remote(req);
        return io_msg_install_complete(req, issue_flags);
}

static int __io_msg_ring_prep(struct io_msg *msg, const struct io_uring_sqe *sqe)
{
        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_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        return __io_msg_ring_prep(io_kiocb_to_cmd(req, struct io_msg), sqe);
}

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_COMPLETE;
}

int io_uring_sync_msg_ring(struct io_uring_sqe *sqe)
{
        struct io_msg io_msg = { };
        int ret;

        ret = __io_msg_ring_prep(&io_msg, sqe);
        if (unlikely(ret))
                return ret;

        /*
         * Only data sending supported, not IORING_MSG_SEND_FD as that one
         * doesn't make sense without a source ring to send files from.
         */
        if (io_msg.cmd != IORING_MSG_DATA)
                return -EINVAL;

        CLASS(fd, f)(sqe->fd);
        if (fd_empty(f))
                return -EBADF;
        if (!io_is_uring_fops(fd_file(f)))
                return -EBADFD;
        return  __io_msg_ring_data(fd_file(f)->private_data,
                                   &io_msg, IO_URING_F_UNLOCKED);
}