On 10/23/26 13:39, Ilias Apalodimas wrote:
On Fri, 23 Oct 2026 at 14:19, Heinrich Schuchardt
<[email protected]> wrote:

On 10/23/26 09:25, Ilias Apalodimas wrote:
Hi Heinrich

On Fri, 23 Oct 2026 at 02:56, Heinrich Schuchardt
<[email protected]> wrote:

* Add missing parameter checks required by the UEFI spec.
* 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 <[email protected]>
---
v3:
          Update commit message to indicate that parameter checks are added.
          Correct a misspelled variable.
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..47325f7d8aa 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)

This is always going to be true since u16_strsize() include the
terminator. It's a nit so I am fine fixing it during the merge

Reviewed-by: Ilias Apalodimas <[email protected]>

string is the pointer variable passed into GetString().
The value of string is not changed by our implementation.

The UEFI specification allows to call the GetString() service with

      String == NULL && StringLength == 0

to retrieve the length of the buffer before allocating a buffer for it.
We must not call memcpy() if string is NULL.

I am not sure I follow you here. If string is NULL, aren't we exiting
really early at the beginning of the function?

Thanks
/Ilias


For String == NULL && *StringLength == 0 (I forgot the * above) the term

    (*string_size && !string)

is not true and we don't quit with EFI_INVALID_PARAMETER. Instead we reach the loop where we look for a string matching the string ID.

We even have a test for this in
lib/efi_selftest/efi_selftest_hii.c:766ff.

Best regards

Heinrich


+                                       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



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