wast: Fix pointer provenance bug reported by MIRI (#1386)

* wast: Fix pointer provenance bug reported by MIRI

We need to re-derive the str pointer after moving the original `Box<str>` it was
derived from.

* wast: Remove all unsafe, use bumpalo for arena

This removes the single unsafe block from the `wast` crate. The unsafe block was
extending the lifetime of some data by moving into an ad-hoc arena. We replace
that usage with `bumpalo`, which is well-tested, vetted, and etc...

* Default all crates in the workspace to `deny(unsafe_code)`

A couple crates still contain unsafe code: one block in `wasmparser` and all
throughout the C API. These have comments explaining their safety.

The one unsafe block that used to exist in `wasm-smith` has been removed. It was
an optimization to avoid double UTF-8 validation when constructing a `str` from
bytes. We simply validate twice now, since that cost should be negligible in the
context of the full Wasm test case generation.

* cargo fmt

Author: fitzgen

Cargo.lock

@@ -12,6 +12,9 @@ repository = "https://github.com/bytecodealliance/wasm-tools"
 readme = "README.md"
 exclude = ['tests/wabt', 'tests/testsuite', 'tests/snapshots', 'ci']
 
+[lints]
+workspace = true
+
 [workspace]
 members = [
   'crates/c-api',
@@ -21,6 +24,12 @@ members = [
   'crates/wit-parser/fuzz',
 ]
 
+[workspace.lints.rust]
+unsafe_code = "deny"
+
+[workspace.lints.clippy]
+all = "allow"
+
 [workspace.package]
 edition = '2021'
 

Cargo.toml

@@ -17,6 +17,9 @@ doc = false
 test = false
 doctest = false
 
+[lints]
+workspace = true
+
 [dependencies]
 arbitrary = { workspace = true, features = ["derive"] }
 wasm-mutate = { workspace = true }

crates/c-api/Cargo.toml

@@ -5,6 +5,9 @@
 //! files of the `include` directory for this crate.
 
 #![allow(non_snake_case, non_camel_case_types, non_upper_case_globals)]
+// This crate fundamentally is doing a lot of unsafe FFI and stuff like that, so
+// it doesn't make sense to allow each individual unsafe block.
+#![allow(unsafe_code)]
 
 use arbitrary::{Error, Unstructured};
 use wasm_smith::{Config, Module};

crates/c-api/src/lib.rs

@@ -12,6 +12,9 @@ rand = { workspace = true }
 wasm-smith = { workspace = true }
 wasmtime = { workspace = true }
 
+[lints]
+workspace = true
+
 [lib]
 doctest = false
 test = false

crates/fuzz-stats/Cargo.toml

@@ -10,6 +10,9 @@ homepage = "https://github.com/bytecodealliance/wasm-tools/tree/main/crates/wasm
 documentation = "https://docs.rs/wasm-compose"
 description = "A library for composing WebAssembly components."
 
+[lints]
+workspace = true
+
 [dependencies]
 wat = { workspace = true }
 wasm-encoder = { workspace = true, features = ['wasmparser'] }

crates/wasm-compose/Cargo.toml

@@ -12,6 +12,9 @@ description = """
 A low-level WebAssembly encoder.
 """
 
+[lints]
+workspace = true
+
 [dependencies]
 leb128 = { workspace = true }
 

crates/wasm-encoder/Cargo.toml

@@ -6,6 +6,9 @@ license = "Apache-2.0 WITH LLVM-exception"
 repository = "https://github.com/bytecodealliance/wasm-tools/tree/main/crates/wasm-metadata"
 description = "Read and manipulate WebAssembly metadata"
 
+[lints]
+workspace = true
+
 [dependencies]
 clap = { workspace = true, optional = true }
 anyhow = { workspace = true }

crates/wasm-metadata/Cargo.toml

@@ -4,6 +4,9 @@ version = "0.1.0"
 edition.workspace = true
 publish = false
 
+[lints]
+workspace = true
+
 [dependencies]
 anyhow = { workspace = true }
 arbitrary = { workspace = true }

crates/wasm-mutate-stats/Cargo.toml

@@ -6,6 +6,9 @@ license = "Apache-2.0 WITH LLVM-exception"
 repository = "https://github.com/bytecodealliance/wasm-tools/tree/main/crates/wasm-mutate"
 description = "A WebAssembly test case mutator"
 
+[lints]
+workspace = true
+
 [dependencies]
 clap = { workspace = true, optional = true }
 thiserror = "1.0.28"