Re: [PATCH] efi: Only print errors about failing to get certs if EFI vars are found

Hello Hans,

Thanks a lot for your feedback.

On 11/19/19 11:59 AM, Hans de Goede wrote:

Hi,

On 19-11-2019 10:18, Javier Martinez Canillas wrote:

quoted

If CONFIG_LOAD_UEFI_KEYS is enabled, the kernel attempts to load the certs
from the db, dbx and MokListRT EFI variables into the appropriate keyrings.

But it just assumes that the variables will be present and prints an error
if the certs can't be loaded, even when is possible that the variables may
not exist. For example the MokListRT variable will only be present if shim
is used.

So only print an error message about failing to get the certs list from an
EFI variable if this is found. Otherwise these printed errors just pollute
the kernel ring buffer with confusing messages like the following:

[    5.427251] Couldn't get size: 0x800000000000000e
[    5.427261] MODSIGN: Couldn't get UEFI db list
[    5.428012] Couldn't get size: 0x800000000000000e
[    5.428023] Couldn't get UEFI MokListRT

Reported-by: Hans de Goede <redacted>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

Thanks for this, I just noticed a potential issue which I missed
when you send this to me for testing:

[snip]

quoted

  
  	if (!efi.get_variable)

@@ -153,8 +156,8 @@ static int __init load_uefi_certs(void)
  	 * an error if we can't get them.
  	 */
  	if (!uefi_check_ignore_db()) {
-		db = get_cert_list(L"db", &secure_var, &dbsize);
-		if (!db) {
+		db = get_cert_list(L"db", &secure_var, &dbsize, &status);
+		if (!db && status != EFI_NOT_FOUND) {
  			pr_err("MODSIGN: Couldn't get UEFI db list\n");
  		} else {
  			rc = parse_efi_signature_list("UEFI:db",

You are correct, this is another instance of the same issue that you mentioned.

quoted

@@ -166,8 +169,8 @@ static int __init load_uefi_certs(void)
  		}
  	}
  
-	mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
-	if (!mok) {
+	mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status);
+	if (!mok && status != EFI_NOT_FOUND) {
  		pr_info("Couldn't get UEFI MokListRT\n");
  	} else {
  		rc = parse_efi_signature_list("UEFI:MokListRT",

This means that if status == EFI_NOT_FOUND we end up still
trying to parse the signature list, I guess that moksize == 0
or some such is saving us here, but I believe that
this should really be:

	if (!mok) {
		if (status != EFI_NOT_FOUND)
			pr_info("Couldn't get UEFI MokListRT\n");
	} else {
		rc = parse_efi_signature_list("UEFI:MokListRT",

Agreed. I'll fix the issues and post a v2. Since we are adding these statements,
I could also print debug messages for the case that status == EFI_NOT_FOUND.

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat