Re: [PATCH 0/1] rust: block: mq: make GenDisk Send impl sound

[Andreas Hindborg <a.hindborg@kernel.org>]

Andreas Hindborg <a.hindborg@kernel.org> writes:

> Hi,
>
> Yuan Tan <ytan089@ucr.edu> writes:
>
>> Hi Linux kernel maintainers,
>>
>> We are developing a tool called FerroLens to detect potential unsound
>> behavior in Rust code in the Linux kernel. FerroLens reported the following
>> bug in rust/kernel/gendisk.rs.
>>
>> Gendisk is marked as Send although the fields it contains may not be.
>> Specifically, the QueueData held in the raw gendisk pointer may not be safe
>> to send across threads. Therefore, sending the Gendisk from one thread to
>> another and dropping on a different thread may cause unsound behavior.
>>
>> Additionally, Gendisk contains an Arc<TagSet<T>>. This Arc would be Send
>> and Sync if the underlying TagSet<T> were Send and Sync. But this is not
>> explicitly derived, although it can be, since the API does not modify the
>> TagSet.
>
> Thanks for the patch. The `GenDisk` `Send` fix looks correct to me.

Actually, I think we need a bound on the Arc as well:

  unsafe impl<T> Send for GenDisk<T>
  where
      T: Operations,
      T::QueueData: Send,
      Arc<TagSet<T>>: Send,
  {
  }

Best regards,
Andreas Hindborg