feat: when deserialization of module from filesystem cache fails, remove from cache

crates/common/src/result.rs

@@ -33,6 +33,10 @@ pub enum WasmErrorInner {
     /// Wasmer failed to build a Module from wasm byte code.
     /// With the feature `wasmer_sys` enabled, building a Module includes compiling the wasm.
     ModuleBuild(String),
+    /// Wasmer failed to serialize a Module to bytes.
+    ModuleSerialize(String),
+    /// Wasmer failed to deserialize a Module from bytes.
+    ModuleDeserialize(String),
     /// The host failed to call a function in the guest.
     CallError(String),
 }
@@ -49,8 +53,10 @@ impl WasmErrorInner {
             | Self::ErrorWhileError
             // Bad memory is bad memory.
             | Self::Memory
-            // Failing to build the wasmer Module means we cannot use it.
+            // Failing to build, serialize, or deserialize the wasmer Module means we cannot use it.
             | Self::ModuleBuild(_)
+            | Self::ModuleSerialize(_)
+            | Self::ModuleDeserialize(_)
             // This is ambiguous so best to treat as potentially corrupt.
             | Self::CallError(_)
              => true,

crates/host/src/module.rs

@@ -197,10 +197,21 @@ impl ModuleCache {
         match self.get_from_filesystem_cache(key) {
             // Filesystem cache hit, deserialize and save to deserialized cache
             Ok(Some(serialized_module)) => {
-                let module = Arc::new(
-                    unsafe { Module::deserialize(&self.runtime_engine, serialized_module.clone()) }
-                        .map_err(|e| wasm_error!(WasmErrorInner::ModuleBuild(e.to_string())))?,
-                );
+                let module_result =
+                    unsafe { Module::deserialize(&self.runtime_engine, serialized_module.clone()) };
+
+                // If deserialization fails, we assume the file is corrupt,
+                // so it is removed from the filesystem cache.
+                let module = match module_result {
+                    Ok(d) => Ok(Arc::new(d)),
+                    Err(e) => {
+                        let _ = self.remove_from_filesystem_cache(key);
+                        Err(wasm_error!(WasmErrorInner::ModuleDeserialize(
+                            e.to_string()
+                        )))
+                    }
+                }?;
+
                 self.add_to_deserialized_cache(key, module.clone());
 
                 Ok(module)
@@ -234,8 +245,9 @@ impl ModuleCache {
                     .serialize()
                     .map_err(|e| wasm_error!(WasmErrorInner::ModuleBuild(e.to_string())))?;
                 let module = Arc::new(unsafe {
-                    Module::deserialize(&self.runtime_engine, serialized_module.clone())
-                        .map_err(|e| wasm_error!(WasmErrorInner::ModuleBuild(e.to_string())))?
+                    Module::deserialize(&self.runtime_engine, serialized_module.clone()).map_err(
+                        |e| wasm_error!(WasmErrorInner::ModuleDeserialize(e.to_string())),
+                    )?
                 });
 
                 // Save serialized module to filesystem cache
@@ -311,6 +323,14 @@ impl ModuleCache {
         Ok(())
     }
 
+    // Remove serialized module from filesystem cache
+    fn remove_from_filesystem_cache(&self, key: CacheKey) -> Result<(), std::io::Error> {
+        if let Some(fs_path) = self.filesystem_cache_module_path(key) {
+            std::fs::remove_file(fs_path)?;
+        }
+
+        Ok(())
+    }
     /// Check deserialized cache for module
     fn get_from_deserialized_cache(&self, key: CacheKey) -> Option<Arc<Module>> {
         let mut deserialized_cache = self.deserialized_module_cache.write();

crates/host/src/module/wasmer_sys.rs

@@ -220,4 +220,71 @@ mod tests {
 
         std::fs::remove_dir_all(tmp_fs_cache_dir).unwrap();
     }
+
+    #[test]
+    fn cache_get_from_fs_corrupt() {
+        // simple example wasm taken from wasmer docs
+        // https://docs.rs/wasmer/latest/wasmer/struct.Module.html#example
+        let wasm: Vec<u8> = vec![
+            0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x06, 0x01, 0x60, 0x01, 0x7f,
+            0x01, 0x7f, 0x03, 0x02, 0x01, 0x00, 0x07, 0x0b, 0x01, 0x07, 0x61, 0x64, 0x64, 0x5f,
+            0x6f, 0x6e, 0x65, 0x00, 0x00, 0x0a, 0x09, 0x01, 0x07, 0x00, 0x20, 0x00, 0x41, 0x01,
+            0x6a, 0x0b, 0x00, 0x1a, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x01, 0x0a, 0x01, 0x00, 0x07,
+            0x61, 0x64, 0x64, 0x5f, 0x6f, 0x6e, 0x65, 0x02, 0x07, 0x01, 0x00, 0x01, 0x00, 0x02,
+            0x70, 0x30,
+        ];
+
+        // Bad serialized_wasm
+        let bad_serialized_wasm = vec![0x00];
+
+        let tmp_fs_cache_dir = tempdir().unwrap().into_path();
+        let module_cache = ModuleCache::new(make_engine, Some(tmp_fs_cache_dir.clone()));
+        let key: CacheKey = [0u8; 32];
+
+        // Build module, serialize, save directly to filesystem
+        let serialized_module_path = tmp_fs_cache_dir.clone().join(hex::encode(key));
+        let mut file = std::fs::OpenOptions::new()
+            .write(true)
+            .create_new(true)
+            .open(&serialized_module_path)
+            .unwrap();
+        file.write_all(&bad_serialized_wasm).unwrap();
+
+        // Module cannot be retrieved from fs cache
+        let res = module_cache.get(key, &wasm);
+        assert!(res.is_err());
+
+        let compiler_engine = make_engine();
+        let module =
+            std::sync::Arc::new(Module::from_binary(&compiler_engine, wasm.as_slice()).unwrap());
+        let serialized_module = module.serialize().unwrap();
+
+        // 2nd time, module can be retrieved from cache
+        let res = module_cache.get(key, &wasm).unwrap();
+        assert_eq!(*res.serialize().unwrap(), *serialized_module);
+
+        // make sure module is stored in deserialized cache
+        {
+            let deserialized_cached_module = module_cache
+                .deserialized_module_cache
+                .write()
+                .get_item(&key)
+                .unwrap();
+            assert_eq!(
+                *deserialized_cached_module.serialize().unwrap(),
+                *module.serialize().unwrap()
+            );
+        }
+
+        // make sure module has been stored in serialized filesystem cache
+        {
+            let serialized_module_path = module_cache
+                .serialized_filesystem_cache_path
+                .unwrap()
+                .join(hex::encode(key));
+            assert!(std::fs::metadata(serialized_module_path).is_ok());
+        }
+
+        std::fs::remove_dir_all(tmp_fs_cache_dir).unwrap();
+    }
 }