Merge #809

809: Fix issue 800 - check index before accessing imports.globals r=syrusakbary a=pventuzelo

# Description

Fix issue #800 

* Check if `import_global_index` is valid i.e inside imports.globals range. 
* Related functions: 
  * validate_memories
  * validate_tables
  * finalize_memories
  * finalize_tables

# After the fix

``` sh
$ ./target/release/wasmer run index_oob_LocalBacking_validate_memories_152.wasm
execute_wasm: "Can\'t instantiate module: LinkError([Generic { message: \"incorrect global index for initializer\" }])"
--------------------------------------------------------------------------------------------------------
$ ./target/release/wasmer run index_oob_LocalBacking_validate_tables_276.wasm 
execute_wasm: "Can\'t instantiate module: LinkError([Generic { message: \"incorrect global index for initializer\" }])"
```

# Review

- [x] Create a short description of the the change in the CHANGELOG.md file


Co-authored-by: Patrick Ventuzelo <ventuzelo.patrick@gmail.com>
Co-authored-by: Patrick Ventuzelo <9038181+pventuzelo@users.noreply.github.com>

Author: bors[bot]

CHANGELOG.md

@@ -6,6 +6,7 @@ Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
 
+- [#809](https://github.com/wasmerio/wasmer/pull/809) Fix bugs leading to panics in `LocalBacking`.
 - [#822](https://github.com/wasmerio/wasmer/pull/822) Update Cranelift fork version to `0.43.1`
 - [#829](https://github.com/wasmerio/wasmer/pull/829) Fix deps on `make bench-*` commands; benchmarks don't compile other backends now
 - [#807](https://github.com/wasmerio/wasmer/pull/807) Implement Send for `Instance`, breaking change on `ImportObject`, remove method `get_namespace` replaced with `with_namespace` and `maybe_with_namespace`

lib/runtime-core/src/backing.rs

@@ -152,6 +152,11 @@ impl LocalBacking {
                     }]);
                 }
                 Initializer::GetGlobal(import_global_index) => {
+                    if import_global_index.index() >= imports.globals.len() {
+                        return Err(vec![LinkError::Generic {
+                            message: "incorrect global index for initializer".to_string(),
+                        }]);
+                    }
                     if let Value::I32(x) = imports.globals[import_global_index].get() {
                         x as u32
                     } else {
@@ -208,6 +213,11 @@ impl LocalBacking {
                     }]);
                 }
                 Initializer::GetGlobal(import_global_index) => {
+                    if import_global_index.index() >= imports.globals.len() {
+                        return Err(vec![LinkError::Generic {
+                            message: "incorrect global index for initializer".to_string(),
+                        }]);
+                    }
                     if let Value::I32(x) = imports.globals[import_global_index].get() {
                         x as u32
                     } else {
@@ -276,6 +286,11 @@ impl LocalBacking {
                     }]);
                 }
                 Initializer::GetGlobal(import_global_index) => {
+                    if import_global_index.index() >= imports.globals.len() {
+                        return Err(vec![LinkError::Generic {
+                            message: "incorrect global index for initializer".to_string(),
+                        }]);
+                    }
                     if let Value::I32(x) = imports.globals[import_global_index].get() {
                         x as u32
                     } else {
@@ -329,6 +344,11 @@ impl LocalBacking {
                     }]);
                 }
                 Initializer::GetGlobal(import_global_index) => {
+                    if import_global_index.index() >= imports.globals.len() {
+                        return Err(vec![LinkError::Generic {
+                            message: "incorrect global index for initializer".to_string(),
+                        }]);
+                    }
                     if let Value::I32(x) = imports.globals[import_global_index].get() {
                         x as u32
                     } else {