Re: [PATCH bpf-next v2 15/28] bpf/hid: add new BPF type to trigger commands from userspace

On Fri, Mar 4, 2022 at 9:33 AM Benjamin Tissoires benjamin.tissoires@redhat.com wrote:

Given that we can not call bpf_hid_raw_request() from within an IRQ, userspace needs to have a way to communicate with the device when it needs.

Implement a new type that the caller can run at will without being in an IRQ context.

Signed-off-by: Benjamin Tissoires benjamin.tissoires@redhat.com

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[...]

•   if (user_size_out && data_out) {
  

•           user_size_out = min3(user_size_out, (u32)ctx->size, (u32)ctx->allocated_size);
  

•           if (copy_to_user(data_out, ctx->data, user_size_out)) {
  

•                   ret = -EFAULT;
  

•                   goto unlock;
  

•           }
  

•           if (copy_to_user(&uattr->test.data_size_out,
  

•                            &user_size_out,
  

•                            sizeof(user_size_out))) {
  

•                   ret = -EFAULT;
  

•                   goto unlock;
  

•           }
  

•   }
  

•   if (copy_to_user(&uattr->test.retval, &ctx->u.user.retval, sizeof(ctx->u.user.retval))) {
  

•           ret = -EFAULT;
  

•           goto unlock;
  

nit: this goto is not really needed.

•   }
  

+unlock:

•   kfree(ctx);
  

•   mutex_unlock(&bpf_hid_mutex);
  

•   return ret;
  

+}

[...]