linux-kernel - Re: [RFC PATCH v2 01/14] lsm: Only build lsm_audit.c if CONFIG

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Message-ID: <CAHC9VhShPEpM4_fPoTSqStMnMB0-n1m6scS5b0Syj5V4RvrFOA@mail.gmail.com>
Date: Tue, 22 Oct 2024 20:07:00 -0400
From: Paul Moore <paul@...l-moore.com>
To: Mickaël Salaün <mic@...ikod.net>
Cc: Eric Paris <eparis@...hat.com>, Günther Noack <gnoack@...gle.com>, 
	"Serge E . Hallyn" <serge@...lyn.com>, Ben Scarlato <akhna@...gle.com>, 
	Casey Schaufler <casey@...aufler-ca.com>, Charles Zaffery <czaffery@...lox.com>, 
	James Morris <jmorris@...ei.org>, Jann Horn <jannh@...gle.com>, Jeff Xu <jeffxu@...gle.com>, 
	Jorge Lucangeli Obes <jorgelo@...gle.com>, Kees Cook <kees@...nel.org>, 
	Konstantin Meskhidze <konstantin.meskhidze@...wei.com>, Matt Bobrowski <mattbobrowski@...gle.com>, 
	Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>, 
	Praveen K Paladugu <prapal@...ux.microsoft.com>, Robert Salvet <robert.salvet@...lox.com>, 
	Shervin Oloumi <enlightened@...gle.com>, Song Liu <song@...nel.org>, 
	Tahera Fahimi <fahimitahera@...il.com>, audit@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [RFC PATCH v2 01/14] lsm: Only build lsm_audit.c if CONFIG_AUDIT
 is set

On Tue, Oct 22, 2024 at 12:10 PM Mickaël Salaün <mic@...ikod.net> wrote:
>
> When CONFIG_AUDIT is set, its CONFIG_NET dependency is also set, and the
> dev_get_by_index and init_net symbols (used by dump_common_audit_data)
> are found by the linker.  dump_common_audit_data() should then failed to
> build when CONFIG_NET is not set. However, because the compiler is
> smart, it knows that audit_log_start() always return NULL when
> !CONFIG_AUDIT, and it doesn't build the body of common_lsm_audit().  As
> a side effect, dump_common_audit_data() is not built and the linker
> doesn't error out because of missing symbols.
>
> Let's only build lsm_audit.o when CONFIG_AUDIT is set.
>
> ipv4_skb_to_auditdata() and ipv6_skb_to_auditdata() are only used by
> Smack if CONFIG_AUDIT is set, so they don't need fake implementations.
>
> Because common_lsm_audit() is used in multiple places without
> CONFIG_AUDIT checks, add a fake implementation.
>
> Cc: Casey Schaufler <casey@...aufler-ca.com>
> Cc: James Morris <jmorris@...ei.org>
> Cc: Paul Moore <paul@...l-moore.com>
> Cc: Serge E. Hallyn <serge@...lyn.com>
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Link: https://lore.kernel.org/r/20241022161009.982584-2-mic@digikod.net
> ---
>  include/linux/lsm_audit.h | 14 ++++++++++++++
>  security/Makefile         |  2 +-
>  2 files changed, 15 insertions(+), 1 deletion(-)

I think this fix is the right thing to do regardless of the rest of
the patchset so I've merged it into lsm/dev, if anyone objects please
speak up.

Thanks!

-- 
paul-moore.com