[PATCH v2 1/1] efi_loader: fix HII GetString()

[Heinrich Schuchardt]

* Add missing conformance tests.
* Return EFI_INVALID_LANGUAGE if a string does not exist in the requested
  language.
* Handle querying the string size with *string_size == 0 and string = NULL.

Fixes: c9bfb22296b0 ("efi_loader: Initial HII database protocols")
Signed-off-by: Heinrich Schuchardt <heinrich.schucha...@canonical.com>
---
v2:
        string_id == 0 is not used by our code. Return EFI_NOT_FOUND.
---
 lib/efi_loader/efi_hii.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/lib/efi_loader/efi_hii.c b/lib/efi_loader/efi_hii.c
index 90dff91e5d4..dc02d7d2ba6 100644
--- a/lib/efi_loader/efi_hii.c
+++ b/lib/efi_loader/efi_hii.c
@@ -910,41 +910,55 @@ get_string(const struct efi_hii_string_protocol *this,
 {
        struct efi_hii_packagelist *hii = package_list;
        struct efi_string_table *stbl;
+       efi_status_t ret;
 
        EFI_ENTRY("%p, \"%s\", %p, %u, %p, %p, %p", this, language,
                  package_list, string_id, string, string_size,
                  string_font_info);
 
-       if (!package_list || !efi_hii_packagelist_exists(package_list))
-               return EFI_EXIT(EFI_NOT_FOUND);
+       if (!language || !string_size || (*string_size && !string)) {
+               ret = EFI_INVALID_PARAMETER;
+               goto out;
+       }
+
+       if (!package_list ||
+           !efi_hii_packagelist_exists(package_list) ||
+           !string id ||
+           string_id > hii->max_string_id) {
+               ret = EFI_NOT_FOUND;
+               goto out;
+       }
 
+       ret = EFI_INVALID_LANGUAGE;
        list_for_each_entry(stbl, &hii->string_tables, link) {
                if (language_match((char *)language, stbl->language)) {
                        efi_string_t str;
                        size_t len;
 
                        if (stbl->nstrings < string_id)
-                               return EFI_EXIT(EFI_NOT_FOUND);
+                               goto out;
 
                        str = stbl->strings[string_id - 1].string;
                        if (str) {
                                len = u16_strsize(str);
                                if (*string_size < len) {
                                        *string_size = len;
-
-                                       return EFI_EXIT(EFI_BUFFER_TOO_SMALL);
+                                       ret = EFI_BUFFER_TOO_SMALL;
+                                       goto out;
                                }
-                               memcpy(string, str, len);
                                *string_size = len;
+                               if (string)
+                                       memcpy(string, str, len);
+                               ret = EFI_SUCCESS;
+                               goto out;
                        } else {
-                               return EFI_EXIT(EFI_NOT_FOUND);
+                               goto out;
                        }
-
-                       return EFI_EXIT(EFI_SUCCESS);
                }
        }
 
-       return EFI_EXIT(EFI_NOT_FOUND);
+out:
+       return EFI_EXIT(ret);
 }
 
 static efi_status_t EFIAPI
-- 
2.53.0