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io: fix unsound pin projection in read_buf and write_buf #2612

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merged 1 commit into from
Jun 12, 2020
Merged

io: fix unsound pin projection in read_buf and write_buf #2612

merged 1 commit into from
Jun 12, 2020

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taiki-e
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@taiki-e taiki-e commented Jun 12, 2020

Motivation

// safety: no data is moved from self
unsafe {
let me = self.get_unchecked_mut();
Pin::new_unchecked(&mut *me.writer).poll_write_buf(cx, &mut me.buf)
}

This is a Pin<&mut Type> to Pin<Field> projection and is unsound if W is not Unpin (you can move W after WriteBuf dropped):
https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=c4740885e4bdb8169e6e5e335fca72d6

The correct projection is Pin<&mut Type> to Pin<&mut Field>. In WriteBuf, it is Pin<&mut WriteBuf<'_, W, B>> to Pin<&mut &mut W>, and it needs to add W: Unpin bounds to convert Pin<&mut &mut W> to Pin<&mut W>.

Solution

Add Self: Unpin bounds to AsyncReadExt::read_buf and AsyncWriteExt::write_buf.
This changes the public API, but I don't think there is any other way to fix this.

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Yay Pin unsafety is fun.

@taiki-e taiki-e merged commit 1769f65 into tokio-rs:master Jun 12, 2020
@taiki-e taiki-e deleted the fix-pin branch June 12, 2020 05:28
@Darksonn Darksonn added the I-unsound 💥 A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness label Jun 12, 2020
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Add Self: Unpin bounds to AsyncReadExt::read_buf and AsyncWriteExt::write_buf.
This changes the public API, but I don't think there is any other way to fix this.

Breaking changes are allowed for bugs. In principle it would be enough to add the bound on the Future impl, but I don't think that would be helpful.

hawkw added a commit that referenced this pull request Jul 20, 2020
- docs: misc improvements (#2572, #2658, #2663, #2656, #2647, #2630, #2487, #2621,
  #2624, #2600, #2623, #2622, #2577, #2569, #2589, #2575, #2540, #2564, #2567,
  #2520, #2521, #2572, #2493)
- rt: allow calls to `block_on` inside calls to `block_in_place` that are
  themselves inside `block_on` (#2645)
- net: fix non-portable behavior when dropping `TcpStream` `OwnedWriteHalf` (#2597)
- io: improve stack usage by allocating large buffers on directly on the heap
  (#2634)
- io: fix unsound pin projection in `AsyncReadExt::read_buf` and
  `AsyncWriteExt::write_buf` (#2612)
- io: fix unnecessary zeroing for `AsyncRead` implementors (#2525)
- io: Fix `BufReader` not correctly forwarding `poll_write_buf` (#2654)

- coop: returning `Poll::Pending` no longer decrements the task budget (#2549)

- io: little-endian variants of `AsyncReadExt` and `AsyncWriteExt` methods
  (#1915)
- io: fix panic in `AsyncReadExt::read_line` (#2541)
- task: add [`tracing`] instrumentation to spawned tasks (#2655)
- sync: allow unsized types in `Mutex` and `RwLock` (via `default` constructors)
  (#2615)
- net: add `ToSocketAddrs` implementation for `&[SocketAddr]` (#2604)
- fs: add `OpenOptionsExt` for `OpenOptions` (#2515)
- fs: add `DirBuilder` (#2524)

[`tracing`]: https://crates.io/crates/tracing

Signed-off-by: Eliza Weisman <eliza@buoyant.io>
hawkw added a commit that referenced this pull request Jul 22, 2020
# 0.2.22 (July 2!, 2020)

### Fixes
- docs: misc improvements (#2572, #2658, #2663, #2656, #2647, #2630, #2487, #2621,
  #2624, #2600, #2623, #2622, #2577, #2569, #2589, #2575, #2540, #2564, #2567,
  #2520, #2521, #2493)
- rt: allow calls to `block_on` inside calls to `block_in_place` that are
  themselves inside `block_on` (#2645)
- net: fix non-portable behavior when dropping `TcpStream` `OwnedWriteHalf` (#2597)
- io: improve stack usage by allocating large buffers on directly on the heap
  (#2634)
- io: fix unsound pin projection in `AsyncReadExt::read_buf` and
  `AsyncWriteExt::write_buf` (#2612)
- io: fix unnecessary zeroing for `AsyncRead` implementors (#2525)
- io: Fix `BufReader` not correctly forwarding `poll_write_buf` (#2654)
- io: fix panic in `AsyncReadExt::read_line` (#2541)

### Changes
- coop: returning `Poll::Pending` no longer decrements the task budget (#2549)

### Added
- io: little-endian variants of `AsyncReadExt` and `AsyncWriteExt` methods
  (#1915)
- task: add [`tracing`] instrumentation to spawned tasks (#2655)
- sync: allow unsized types in `Mutex` and `RwLock` (via `default` constructors)
  (#2615)
- net: add `ToSocketAddrs` implementation for `&[SocketAddr]` (#2604)
- fs: add `OpenOptionsExt` for `OpenOptions` (#2515)
- fs: add `DirBuilder` (#2524)

[`tracing`]: https://crates.io/crates/tracing

Signed-off-by: Eliza Weisman <eliza@buoyant.io>
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