linux-kernel - Re: [PATCH v2 1/1] certs: Explain the rationale to call panic()

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Message-ID: <YjoyF02zD5WdAMOW@iki.fi>
Date:   Tue, 22 Mar 2022 22:31:19 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     David Howells <dhowells@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        David Woodhouse <dwmw2@...radead.org>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        Paul Moore <paul@...l-moore.com>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>,
        keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v2 1/1] certs: Explain the rationale to call panic()

On Tue, Mar 22, 2022 at 12:13:23PM +0100, Mickaël Salaün wrote:
> From: Mickaël Salaün <mic@...ux.microsoft.com>
> 
> The blacklist_init() function calls panic() for memory allocation
> errors.  This change documents the reason why we don't return -ENODEV.
> 
> Suggested-by: Paul Moore <paul@...l-moore.com> [1]
> Requested-by: Jarkko Sakkinen <jarkko@...nel.org> [1]
> Link: https://lore.kernel.org/r/YjeW2r6Wv55Du0bJ@iki.fi [1]
> Reviewed-by: Paul Moore <paul@...l-moore.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
> Link: https://lore.kernel.org/r/20220322111323.542184-2-mic@digikod.net
> ---
> 
> Changes since v1:
> * Fix commit subject spelling spotted by David Woodhouse.
> * Reword one sentence as suggested by Paul Moore.
> * Add Reviewed-by Paul Moore.
> * Add Reviewed-by Jarkko Sakkinen.
> ---
>  certs/blacklist.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/certs/blacklist.c b/certs/blacklist.c
> index 486ce0dd8e9c..25094ea73600 100644
> --- a/certs/blacklist.c
> +++ b/certs/blacklist.c
> @@ -307,6 +307,15 @@ static int restrict_link_for_blacklist(struct key *dest_keyring,
>  
>  /*
>   * Initialise the blacklist
> + *
> + * The blacklist_init() function is registered as an initcall via
> + * device_initcall().  As a result if the blacklist_init() function fails for
> + * any reason the kernel continues to execute.  While cleanly returning -ENODEV
> + * could be acceptable for some non-critical kernel parts, if the blacklist
> + * keyring fails to load it defeats the certificate/key based deny list for
> + * signed modules.  If a critical piece of security functionality that users
> + * expect to be present fails to initialize, panic()ing is likely the right
> + * thing to do.
>   */
>  static int __init blacklist_init(void)
>  {
> -- 
> 2.35.1
> 

Thank you, I'll put this into my "queue" folder and apply as soon I have
bandwidth.

BR, Jarkko