linux-kernel - Re: [PATCH v1 1/1] certs: Explain the rational to call panic()

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Message-ID: <CAHC9VhR+Ss5VAUHLutTvyS8g+agZy7d0YGcu_9dV1LBx_8ifNQ@mail.gmail.com>
Date:   Mon, 21 Mar 2022 14:23:54 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        David Howells <dhowells@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        David Woodhouse <dwmw2@...radead.org>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        keyrings@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v1 1/1] certs: Explain the rational to call panic()

On Mon, Mar 21, 2022 at 1:45 PM Mickaël Salaün <mic@...ikod.net> 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]
> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
> Link: https://lore.kernel.org/r/20220321174548.510516-2-mic@digikod.net
> ---
>  certs/blacklist.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

I would suggest changing the second sentence as shown below, but
otherwise it looks good to me.

Reviewed-by: Paul Moore <paul@...l-moore.com>

> diff --git a/certs/blacklist.c b/certs/blacklist.c
> index 486ce0dd8e9c..ac26bcf9b9a5 100644
> --- a/certs/blacklist.c
> +++ b/certs/blacklist.c
> @@ -307,6 +307,14 @@ 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 the functionality doesn't load and the

"As a result if the blacklist_init() function fails for any reason the
kernel continues to execute."

> + * kernel continues on executing.  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)
>  {

--
paul-moore.com