[bug report] ocxl: Add AFU interrupt support

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Frederic Barrat,

The patch aeddad1760ae: "ocxl: Add AFU interrupt support" from Jan
23, 2018, leads to the following static checker warning:

    drivers/misc/ocxl/file.c:163 afu_ioctl()
    warn: maybe return -EFAULT instead of the bytes remaining?

drivers/misc/ocxl/file.c
   111  static long afu_ioctl(struct file *file, unsigned int cmd,
   112                  unsigned long args)
   113  {
   114          struct ocxl_context *ctx = file->private_data;
   115          struct ocxl_ioctl_irq_fd irq_fd;
   116          u64 irq_offset;
   117          long rc;
   118  
   119          pr_debug("%s for context %d, command %s\n", __func__, ctx->pasid,
   120                  CMD_STR(cmd));
   121  
   122          if (ctx->status == CLOSED)
   123                  return -EIO;
   124  
   125          switch (cmd) {
   126          case OCXL_IOCTL_ATTACH:
   127                  rc = afu_ioctl_attach(ctx,
   128                                  (struct ocxl_ioctl_attach __user *) args);
   129                  break;
   130  
   131          case OCXL_IOCTL_IRQ_ALLOC:
   132                  rc = ocxl_afu_irq_alloc(ctx, &irq_offset);
   133                  if (!rc) {
   134                          rc = copy_to_user((u64 __user *) args, &irq_offset,
   135                                          sizeof(irq_offset));
   136                          if (rc)
                                    ^^
copy_to_user() returns the number of bytes remaining but we want to
return -EFAULT on error.

   137                                  ocxl_afu_irq_free(ctx, irq_offset);
   138                  }
   139                  break;
   140  

    drivers/misc/ocxl/file.c:320 afu_read()
    warn: unsigned 'used' is never less than zero.

drivers/misc/ocxl/file.c
   279          ssize_t rc;
   280          size_t used = 0;
                ^^^^^^
This should be ssize_t

   281          DEFINE_WAIT(event_wait);
   282  
   283          memset(&header, 0, sizeof(header));
   284  
   285          /* Require offset to be 0 */
   286          if (*off != 0)
   287                  return -EINVAL;
   288  
   289          if (count < (sizeof(struct ocxl_kernel_event_header) +
   290                          AFU_EVENT_BODY_MAX_SIZE))
   291                  return -EINVAL;
   292  
   293          for (;;) {
   294                  prepare_to_wait(&ctx->events_wq, &event_wait,
   295                                  TASK_INTERRUPTIBLE);
   296  
   297                  if (afu_events_pending(ctx))
   298                          break;
   299  
   300                  if (ctx->status == CLOSED)
   301                          break;
   302  
   303                  if (file->f_flags & O_NONBLOCK) {
   304                          finish_wait(&ctx->events_wq, &event_wait);
   305                          return -EAGAIN;
   306                  }
   307  
   308                  if (signal_pending(current)) {
   309                          finish_wait(&ctx->events_wq, &event_wait);
   310                          return -ERESTARTSYS;
   311                  }
   312  
   313                  schedule();
   314          }
   315  
   316          finish_wait(&ctx->events_wq, &event_wait);
   317  
   318          if (has_xsl_error(ctx)) {
   319                  used = append_xsl_error(ctx, &header, buf + sizeof(header));
   320                  if (used < 0)
                            ^^^^^^^^
Impossible.

   321                          return used;
   322          }
   323  
   324          if (!afu_events_pending(ctx))
   325                  header.flags |= OCXL_KERNEL_EVENT_FLAG_LAST;
   326  
   327          if (copy_to_user(buf, &header, sizeof(header)))
   328                  return -EFAULT;
   329  
   330          used += sizeof(header);
   331  
   332          rc = (ssize_t) used;
                     ^^^^^^^^^^^^^^
You could remove the cast.

   333          return rc;
   334  }

regards,
dan carpenter