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

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Message-ID: <Y3QnNwWrOjpNwZ6r@kernel.org>
Date:   Wed, 16 Nov 2022 01:56:39 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Mickaël Salaün <mic@...ikod.net>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        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: Re: [PATCH v2 3/3] certs: don't try to update blacklist keys

On Wed, Nov 09, 2022 at 03:50:19AM +0100, Thomas Weißschuh wrote:
> When the same key is blacklisted repeatedly we don't want to log an

Who is "we"?

> 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.

How? I.e. please state how you extend it, and why new need the extra bits.

> 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
> 

BR, Jarkko