Fix segfault with custom page sizes on aarch64

crates/environ/src/compile/module_environ.rs

@@ -996,9 +996,20 @@ impl ModuleTranslation<'_> {
 
         // Validate that the memory information collected is indeed valid for
         // static memory initialization.
-        for info in info.values().filter(|i| i.data_size > 0) {
+        for (i, info) in info.iter().filter(|(_, info)| info.data_size > 0) {
             let image_size = info.max_addr - info.min_addr;
 
+            // Simplify things for now by bailing out entirely if any memory has
+            // a page size smaller than the host's page size. This fixes a case
+            // where currently initializers are created in host-page-size units
+            // of length which means that a larger-than-the-entire-memory
+            // initializer can be created. This can be handled technically but
+            // would require some more changes to help fix the assert elsewhere
+            // that this protects against.
+            if self.module.memory_plans[i].memory.page_size() < page_size {
+                return;
+            }
+
             // If the range of memory being initialized is less than twice the
             // total size of the data itself then it's assumed that static
             // initialization is ok. This means we'll at most double memory

crates/wasmtime/src/runtime/vm/instance/allocator.rs

@@ -732,7 +732,11 @@ fn initialize_memories(instance: &mut Instance, module: &Module) -> Result<()> {
 
             unsafe {
                 let src = self.instance.wasm_data(init.data.clone());
-                let dst = memory.base.add(usize::try_from(init.offset).unwrap());
+                let offset = usize::try_from(init.offset).unwrap();
+                let dst = memory.base.add(offset);
+
+                assert!(offset + src.len() <= memory.current_length());
+
                 // FIXME audit whether this is safe in the presence of shared
                 // memory
                 // (https://github.com/bytecodealliance/wasmtime/issues/4203).

tests/wast.rs

@@ -294,8 +294,10 @@ fn run_wast(wast: &Path, strategy: Strategy, pooling: bool) -> anyhow::Result<()
             cfg.static_memory_maximum_size(0);
         }
         cfg.dynamic_memory_reserved_for_growth(0);
-        cfg.static_memory_guard_size(0);
-        cfg.dynamic_memory_guard_size(0);
+
+        let small_guard = 64 * 1024;
+        cfg.static_memory_guard_size(small_guard);
+        cfg.dynamic_memory_guard_size(small_guard);
     }
 
     let _pooling_lock = if pooling {