Backport soundness fix

embassy-executor-macros/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "embassy-executor-macros"
-version = "0.4.1"
+version = "0.4.2"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "macros for creating the entry point and tasks for embassy-executor"
@@ -13,7 +13,7 @@ categories = [
 ]
 
 [dependencies]
-syn = { version = "2.0.15", features = ["full", "extra-traits"] }
+syn = { version = "2.0.15", features = ["full", "visit"] }
 quote = "1.0.9"
 darling = "0.20.1"
 proc-macro2 = "1.0.29"

embassy-executor-macros/src/macros/task.rs

@@ -2,6 +2,7 @@ use darling::export::NestedMeta;
 use darling::FromMeta;
 use proc_macro2::{Span, TokenStream};
 use quote::{format_ident, quote};
+use syn::visit::Visit;
 use syn::{parse_quote, Expr, ExprLit, ItemFn, Lit, LitInt, ReturnType, Type};
 
 use crate::util::ctxt::Ctxt;
@@ -57,15 +58,18 @@ pub fn run(args: &[NestedMeta], f: syn::ItemFn) -> Result<TokenStream, TokenStre
             syn::FnArg::Receiver(_) => {
                 ctxt.error_spanned_by(arg, "task functions must not have receiver arguments");
             }
-            syn::FnArg::Typed(t) => match t.pat.as_mut() {
-                syn::Pat::Ident(id) => {
-                    id.mutability = None;
-                    args.push((id.clone(), t.attrs.clone()));
+            syn::FnArg::Typed(t) => {
+                check_arg_ty(&t.ty)?;
+                match t.pat.as_mut() {
+                    syn::Pat::Ident(id) => {
+                        id.mutability = None;
+                        args.push((id.clone(), t.attrs.clone()));
+                    }
+                    _ => {
+                        ctxt.error_spanned_by(arg, "pattern matching in task arguments is not yet supported");
+                    }
                 }
-                _ => {
-                    ctxt.error_spanned_by(arg, "pattern matching in task arguments is not yet supported");
-                }
-            },
+            }
         }
     }
 
@@ -123,3 +127,27 @@ pub fn run(args: &[NestedMeta], f: syn::ItemFn) -> Result<TokenStream, TokenStre
 
     Ok(result)
 }
+
+fn check_arg_ty(ty: &Type) -> Result<(), TokenStream> {
+    struct Visitor {
+        errors: Option<TokenStream>,
+    }
+
+    impl<'ast> Visit<'ast> for Visitor {
+        fn visit_type_impl_trait(&mut self, i: &'ast syn::TypeImplTrait) {
+            use syn::spanned::Spanned;
+            self.errors = Some(quote::quote_spanned! { i.span() =>
+                compile_error!("`impl Trait` is not allowed in task arguments. It is syntax sugar for generics, and tasks can't be generic.");
+            });
+        }
+    }
+
+    let mut visitor = Visitor { errors: None };
+    Visit::visit_type(&mut visitor, ty);
+
+    if let Some(errors) = visitor.errors {
+        Err(errors)
+    } else {
+        Ok(())
+    }
+}

embassy-executor/CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+## 0.5.1 - 2024-10-21
+
+- Soundness fix: Deny using `impl Trait` in task arguments. This was previously accidentally allowed when not using the `nightly` feature,
+  and could cause out of bounds memory accesses if spawning the same task mulitple times with different underlying types
+  for the `impl Trait`.
+
 ## 0.5.0 - 2024-01-11
 
 - Updated to `embassy-time-driver 0.1`, `embassy-time-queue-driver 0.1`, compatible with `embassy-time v0.3` and higher.

embassy-executor/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "embassy-executor"
-version = "0.5.0"
+version = "0.5.1"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "async/await executor designed for embedded usage"
@@ -33,7 +33,7 @@ defmt = { version = "0.3", optional = true }
 log = { version = "0.4.14", optional = true }
 rtos-trace = { version = "0.1.2", optional = true }
 
-embassy-executor-macros = { version = "0.4.0", path = "../embassy-executor-macros" }
+embassy-executor-macros = { version = "0.4.2", path = "../embassy-executor-macros" }
 embassy-time-driver = { version = "0.1.0", path = "../embassy-time-driver", optional = true }
 embassy-time-queue-driver = { version = "0.1.0", path = "../embassy-time-queue-driver", optional = true }
 critical-section = "1.1"