io_uring/msg_ring.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/kernel.h>
   3 #include <linux/errno.h>
   4 #include <linux/file.h>
   5 #include <linux/slab.h>
   6 #include <linux/nospec.h>
   7 #include <linux/io_uring.h>
   8
   9 #include <uapi/linux/io_uring.h>
  10
  11 #include "io_uring.h"
  12 #include "rsrc.h"
  13 #include "filetable.h"
  14 #include "msg_ring.h"
  15
  16 struct io_msg {
  17         struct file                     *file;
  18         u64 user_data;
  19         u32 len;
  20         u32 cmd;
  21         u32 src_fd;
  22         u32 dst_fd;
  23         u32 flags;
  24 };
  25
  26 static int io_msg_ring_data(struct io_kiocb *req)
  27 {
  28         struct io_ring_ctx *target_ctx = req->file->private_data;
  29         struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
  30
  31         if (msg->src_fd || msg->dst_fd || msg->flags)
  32                 return -EINVAL;
  33
  34         if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
  35                 return 0;
  36
  37         return -EOVERFLOW;
  38 }
  39
  40 static void io_double_unlock_ctx(struct io_ring_ctx *ctx,
  41                                  struct io_ring_ctx *octx,
  42                                  unsigned int issue_flags)
  43 {
  44         if (issue_flags & IO_URING_F_UNLOCKED)
  45                 mutex_unlock(&ctx->uring_lock);
  46         mutex_unlock(&octx->uring_lock);
  47 }
  48
  49 static int io_double_lock_ctx(struct io_ring_ctx *ctx,
  50                               struct io_ring_ctx *octx,
  51                               unsigned int issue_flags)
  52 {
  53         /*
  54          * To ensure proper ordering between the two ctxs, we can only
  55          * attempt a trylock on the target. If that fails and we already have
  56          * the source ctx lock, punt to io-wq.
  57          */
  58         if (!(issue_flags & IO_URING_F_UNLOCKED)) {
  59                 if (!mutex_trylock(&octx->uring_lock))
  60                         return -EAGAIN;
  61                 return 0;
  62         }
  63
  64         /* Always grab smallest value ctx first. We know ctx != octx. */
  65         if (ctx < octx) {
  66                 mutex_lock(&ctx->uring_lock);
  67                 mutex_lock(&octx->uring_lock);
  68         } else {
  69                 mutex_lock(&octx->uring_lock);
  70                 mutex_lock(&ctx->uring_lock);
  71         }
  72
  73         return 0;
  74 }
  75
  76 static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
  77 {
  78         struct io_ring_ctx *target_ctx = req->file->private_data;
  79         struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
  80         struct io_ring_ctx *ctx = req->ctx;
  81         unsigned long file_ptr;
  82         struct file *src_file;
  83         int ret;
  84
  85         if (target_ctx == ctx)
  86                 return -EINVAL;
  87
  88         ret = io_double_lock_ctx(ctx, target_ctx, issue_flags);
  89         if (unlikely(ret))
  90                 return ret;
  91
  92         ret = -EBADF;
  93         if (unlikely(msg->src_fd >= ctx->nr_user_files))
  94                 goto out_unlock;
  95
  96         msg->src_fd = array_index_nospec(msg->src_fd, ctx->nr_user_files);
  97         file_ptr = io_fixed_file_slot(&ctx->file_table, msg->src_fd)->file_ptr;
  98         src_file = (struct file *) (file_ptr & FFS_MASK);
  99         get_file(src_file);
 100
 101         ret = __io_fixed_fd_install(target_ctx, src_file, msg->dst_fd);
 102         if (ret < 0) {
 103                 fput(src_file);
 104                 goto out_unlock;
 105         }
 106
 107         if (msg->flags & IORING_MSG_RING_CQE_SKIP)
 108                 goto out_unlock;
 109
 110         /*
 111          * If this fails, the target still received the file descriptor but
 112          * wasn't notified of the fact. This means that if this request
 113          * completes with -EOVERFLOW, then the sender must ensure that a
 114          * later IORING_OP_MSG_RING delivers the message.
 115          */
 116         if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
 117                 ret = -EOVERFLOW;
 118 out_unlock:
 119         io_double_unlock_ctx(ctx, target_ctx, issue_flags);
 120         return ret;
 121 }
 122
 123 int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 124 {
 125         struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
 126
 127         if (unlikely(sqe->buf_index || sqe->personality))
 128                 return -EINVAL;
 129
 130         msg->user_data = READ_ONCE(sqe->off);
 131         msg->len = READ_ONCE(sqe->len);
 132         msg->cmd = READ_ONCE(sqe->addr);
 133         msg->src_fd = READ_ONCE(sqe->addr3);
 134         msg->dst_fd = READ_ONCE(sqe->file_index);
 135         msg->flags = READ_ONCE(sqe->msg_ring_flags);
 136         if (msg->flags & ~IORING_MSG_RING_CQE_SKIP)
 137                 return -EINVAL;
 138
 139         return 0;
 140 }
 141
 142 int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags)
 143 {
 144         struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
 145         int ret;
 146
 147         ret = -EBADFD;
 148         if (!io_is_uring_fops(req->file))
 149                 goto done;
 150
 151         switch (msg->cmd) {
 152         case IORING_MSG_DATA:
 153                 ret = io_msg_ring_data(req);
 154                 break;
 155         case IORING_MSG_SEND_FD:
 156                 ret = io_msg_send_fd(req, issue_flags);
 157                 break;
 158         default:
 159                 ret = -EINVAL;
 160                 break;
 161         }
 162
 163 done:
 164         if (ret < 0)
 165                 req_set_fail(req);
 166         io_req_set_res(req, ret, 0);
 167         /* put file to avoid an attempt to IOPOLL the req */
 168         if (!(req->flags & REQ_F_FIXED_FILE))
 169                 io_put_file(req->file);
 170         req->file = NULL;
 171         return IOU_OK;
 172 }