wasi-nn: fix buffer overruns in load_by_name/load_by_name_with_config (#4491)

also, ensure NUL terminations here to simplify backend implementations.
(note that, although names with '\0' in the middle are usually valid
in wasm, wamr doesn't support them in general. we might revisit this
later.)

also, add a missing address validation in load_by_name_with_config.

cf. https://github.com/bytecodealliance/wasm-micro-runtime/issues/4487

core/iwasm/libraries/wasi-nn/src/wasi_nn.c

@@ -507,10 +507,35 @@ fail:
     return res;
 }
 
+static wasi_nn_error
+copyin_and_nul_terminate(wasm_module_inst_t inst, char *name, uint32_t name_len,
+                         char **resultp)
+{
+    char *nul_terminated_name;
+    if (!wasm_runtime_validate_native_addr(inst, name, name_len)) {
+        return invalid_argument;
+    }
+    nul_terminated_name = wasm_runtime_malloc(name_len + 1);
+    if (nul_terminated_name == NULL) {
+        return runtime_error;
+    }
+    bh_memcpy_s(nul_terminated_name, name_len + 1, name, name_len);
+    nul_terminated_name[name_len] = '\0'; /* ensure NUL termination */
+    if (strlen(nul_terminated_name) != name_len) {
+        /* reject names containing '\0' for now */
+        wasm_runtime_free(nul_terminated_name);
+        return invalid_argument;
+    }
+    *resultp = nul_terminated_name;
+    return success;
+}
+
 wasi_nn_error
 wasi_nn_load_by_name(wasm_exec_env_t exec_env, char *name, uint32_t name_len,
                      graph *g)
 {
+    WASINNContext *wasi_nn_ctx = NULL;
+    char *nul_terminated_name = NULL;
     wasi_nn_error res;
 
     wasm_module_inst_t instance = wasm_runtime_get_module_inst(exec_env);
@@ -518,25 +543,21 @@ wasi_nn_load_by_name(wasm_exec_env_t exec_env, char *name, uint32_t name_len,
         return runtime_error;
     }
 
-    if (!wasm_runtime_validate_native_addr(instance, name, name_len)) {
-        NN_ERR_PRINTF("name is invalid");
-        return invalid_argument;
-    }
-
     if (!wasm_runtime_validate_native_addr(instance, g,
                                            (uint64)sizeof(graph))) {
         NN_ERR_PRINTF("graph is invalid");
         return invalid_argument;
     }
 
-    if (name_len == 0 || name[name_len] != '\0') {
-        NN_ERR_PRINTF("Invalid filename");
-        return invalid_argument;
+    res = copyin_and_nul_terminate(instance, name, name_len,
+                                   &nul_terminated_name);
+    if (res != success) {
+        goto fail;
     }
 
-    NN_DBG_PRINTF("[WASI NN] LOAD_BY_NAME %s...", name);
+    NN_DBG_PRINTF("[WASI NN] LOAD_BY_NAME %s...", nul_terminated_name);
 
-    WASINNContext *wasi_nn_ctx = lock_ctx(instance);
+    wasi_nn_ctx = lock_ctx(instance);
     if (wasi_nn_ctx == NULL) {
         res = busy;
         goto fail;
@@ -547,14 +568,20 @@ wasi_nn_load_by_name(wasm_exec_env_t exec_env, char *name, uint32_t name_len,
         goto fail;
 
     call_wasi_nn_func(wasi_nn_ctx->backend, load_by_name, res,
-                      wasi_nn_ctx->backend_ctx, name, name_len, g);
+                      wasi_nn_ctx->backend_ctx, nul_terminated_name, name_len,
+                      g);
     if (res != success)
         goto fail;
 
     wasi_nn_ctx->is_model_loaded = true;
     res = success;
 fail:
-    unlock_ctx(wasi_nn_ctx);
+    if (nul_terminated_name != NULL) {
+        wasm_runtime_free(nul_terminated_name);
+    }
+    if (wasi_nn_ctx != NULL) {
+        unlock_ctx(wasi_nn_ctx);
+    }
     return res;
 }
 
@@ -563,6 +590,9 @@ wasi_nn_load_by_name_with_config(wasm_exec_env_t exec_env, char *name,
                                  int32_t name_len, char *config,
                                  int32_t config_len, graph *g)
 {
+    WASINNContext *wasi_nn_ctx = NULL;
+    char *nul_terminated_name = NULL;
+    char *nul_terminated_config = NULL;
     wasi_nn_error res;
 
     wasm_module_inst_t instance = wasm_runtime_get_module_inst(exec_env);
@@ -570,30 +600,27 @@ wasi_nn_load_by_name_with_config(wasm_exec_env_t exec_env, char *name,
         return runtime_error;
     }
 
-    if (!wasm_runtime_validate_native_addr(instance, name, name_len)) {
-        NN_ERR_PRINTF("name is invalid");
-        return invalid_argument;
-    }
-
     if (!wasm_runtime_validate_native_addr(instance, g,
                                            (uint64)sizeof(graph))) {
         NN_ERR_PRINTF("graph is invalid");
         return invalid_argument;
     }
 
-    if (name_len == 0 || name[name_len] != '\0') {
-        NN_ERR_PRINTF("Invalid filename");
-        return invalid_argument;
+    res = copyin_and_nul_terminate(instance, name, name_len,
+                                   &nul_terminated_name);
+    if (res != success) {
+        goto fail;
+    }
+    res = copyin_and_nul_terminate(instance, config, config_len,
+                                   &nul_terminated_config);
+    if (res != success) {
+        goto fail;
     }
 
-    if (!config || config_len == 0 || config[config_len] != '\0') {
-        NN_ERR_PRINTF("Invalid config");
-        return invalid_argument;
-    }
+    NN_DBG_PRINTF("[WASI NN] LOAD_BY_NAME_WITH_CONFIG %s %s...",
+                  nul_terminated_name, nul_terminated_config);
 
-    NN_DBG_PRINTF("[WASI NN] LOAD_BY_NAME_WITH_CONFIG %s %s...", name, config);
-
-    WASINNContext *wasi_nn_ctx = lock_ctx(instance);
+    wasi_nn_ctx = lock_ctx(instance);
     if (wasi_nn_ctx == NULL) {
         res = busy;
         goto fail;
@@ -605,15 +632,23 @@ wasi_nn_load_by_name_with_config(wasm_exec_env_t exec_env, char *name,
     ;
 
     call_wasi_nn_func(wasi_nn_ctx->backend, load_by_name_with_config, res,
-                      wasi_nn_ctx->backend_ctx, name, name_len, config,
-                      config_len, g);
+                      wasi_nn_ctx->backend_ctx, nul_terminated_name, name_len,
+                      nul_terminated_config, config_len, g);
     if (res != success)
         goto fail;
 
     wasi_nn_ctx->is_model_loaded = true;
     res = success;
 fail:
-    unlock_ctx(wasi_nn_ctx);
+    if (nul_terminated_name != NULL) {
+        wasm_runtime_free(nul_terminated_name);
+    }
+    if (nul_terminated_config != NULL) {
+        wasm_runtime_free(nul_terminated_config);
+    }
+    if (wasi_nn_ctx != NULL) {
+        unlock_ctx(wasi_nn_ctx);
+    }
     return res;
 }