efi: pstore: Drop efivar lock when efi_pstore_open() returns with an error

If kzalloc fails, the function returns -ENOMEM without calling
efivar_unlock(). Since open() returned  an error, the calling site
in pstore_get_backend_records() won't call the close() function, so
the lock is never released. Thus drop the lock in case of errors here.

Fixes: 859748255b ("efi: pstore: Omit efivars caching EFI varstore access layer")
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/efi-pstore.c

@@ -60,8 +60,10 @@ static int efi_pstore_open(struct pstore_info *psi)
 		return err;
 
 	psi->data = kzalloc(record_size, GFP_KERNEL);
-	if (!psi->data)
+	if (!psi->data) {
+		efivar_unlock();
 		return -ENOMEM;
+	}
 
 	return 0;
 }