linux-kernel - [PATCH v2 3/3] certs: don't try to update blacklist keys

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Date:   Wed,  9 Nov 2022 03:50:19 +0100
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Mickaël Salaün <mic@...ikod.net>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Eric Snowberg <eric.snowberg@...cle.com>
Cc:     Thomas Weißschuh <linux@...ssschuh.net>,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Pearson <markpearson@...ovo.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: [PATCH v2 3/3] certs: don't try to update blacklist keys

When the same key is blacklisted repeatedly we don't want to log an
error. These duplicates can be provided by buggy firmware. Instead of
spamming the bootlog with errors we use a warning that can still be seen
by OEMs when testing.

Also extend BLACKLIST_KEY_PERM as otherwise the EACCES will shadow the
EEXIST.

Link: https://lore.kernel.org/all/c8c65713-5cda-43ad-8018-20f2e32e4432@t-8ch.de/
Link: https://lore.kernel.org/all/20221104014704.3469-1-linux@weissschuh.net/
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 certs/blacklist.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/certs/blacklist.c b/certs/blacklist.c
index 6e260c4b6a19..ac8e3166b6d7 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -26,7 +26,7 @@
  */
 #define MAX_HASH_LEN	128
 
-#define BLACKLIST_KEY_PERM (KEY_POS_SEARCH | KEY_POS_VIEW | \
+#define BLACKLIST_KEY_PERM (KEY_POS_WRITE | KEY_POS_SEARCH | KEY_POS_VIEW | \
 			    KEY_USR_SEARCH | KEY_USR_VIEW)
 
 static const char tbs_prefix[] = "tbs";
@@ -183,16 +183,19 @@ static int mark_raw_hash_blacklisted(const char *hash)
 {
 	key_ref_t key;
 
-	key = key_create_or_update(make_key_ref(blacklist_keyring, true),
-				   "blacklist",
-				   hash,
-				   NULL,
-				   0,
-				   BLACKLIST_KEY_PERM,
-				   KEY_ALLOC_NOT_IN_QUOTA |
-				   KEY_ALLOC_BUILT_IN);
+	key = key_create(make_key_ref(blacklist_keyring, true),
+			 "blacklist",
+			 hash,
+			 NULL,
+			 0,
+			 BLACKLIST_KEY_PERM,
+			 KEY_ALLOC_NOT_IN_QUOTA |
+			 KEY_ALLOC_BUILT_IN);
 	if (IS_ERR(key)) {
-		pr_err("Problem blacklisting hash %s: %pe\n", hash, key);
+		if (PTR_ERR(key) == -EEXIST)
+			pr_warn("Duplicate blacklisted hash %s\n", hash);
+		else
+			pr_err("Problem blacklisting hash %s: %pe\n", hash, key);
 		return PTR_ERR(key);
 	}
 	return 0;
-- 
2.38.1