dm verity: fallback to platform keyring also if key in trusted keyring is rejected

If enabled, we fallback to the platform keyring if the trusted keyring doesn't have
the key used to sign the roothash. But if pkcs7_verify() rejects the key for other
reasons, such as usage restrictions, we do not fallback. Do so.

Follow-up for 6fce1f40Suggested-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Luca Boccassi <bluca@debian.org>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

drivers/md/dm-verity-verify-sig.c

@@ -127,7 +127,7 @@ int verity_verify_root_hash(const void *root_hash, size_t root_hash_len,
 #endif
 				VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);
 #ifdef CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG_PLATFORM_KEYRING
-	if (ret == -ENOKEY)
+	if (ret == -ENOKEY || ret == -EKEYREJECTED)
 		ret = verify_pkcs7_signature(root_hash, root_hash_len, sig_data,
 					sig_len,
 					VERIFY_USE_PLATFORM_KEYRING,