WASI fd_write and fd_read fails on memory boundary

[subzey]

Describe the bug

WASI fd_write and fd_read fails if the iovec describes a buffer such that its right boundary coincides with the memory right boundary.

Example:

There's 1 page of memory (0x10000 bytes).

Callng fd_read or fd_write with iovec[ 65532, 4 ]:

    FFFC FFFD FFFE FFFF
───┬────┬────┬────┬────╖
...│    │    │    │    ║
───┴────┴────┴────┴────╜
   │←───── len: 4 ────→│
   ↑ offset: 0xFFFC (65532)

The wasm memory size is just enough to fit this buffer. But the call errs with code 21.

If len is changed to 3, it works nicely.

If memory size is changed to 2 (2 * 0x10000 bytes), it works nicely.

wasmer version 0.14.1
OS x86_64 GNU/Linux (Ubuntu 18.04)
Rust compiler is not used.

Steps to reproduce

Run this .wat file with wasmer run

https://gist.github.com/subzey/7dd2cc27274b59322d78878f73a0944d

Expected behavior

It should output TEST into stdout and exit with 0 exit code.

Actual behavior

It outputs nothing and exists with 21.

Additional context

This file executed with wasmtime works as expected.

[syrusakbary]

Thanks for reporting and for the minimal reproduce case, it's super helpful!

We will investigate soon :)