linux-kernel - Re: [PATCH v4 13/17] module: Report signature type to users

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Message-ID: <8d399298-88a6-4c89-a0ed-fed0268b6493@t-8ch.de>
Date: Tue, 3 Feb 2026 13:44:05 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: Nathan Chancellor <nathan@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Luis Chamberlain <mcgrof@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Daniel Gomez <da.gomez@...sung.com>, Paul Moore <paul@...l-moore.com>, 
	James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, 
	Jonathan Corbet <corbet@....net>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
	Naveen N Rao <naveen@...nel.org>, Mimi Zohar <zohar@...ux.ibm.com>, 
	Roberto Sassu <roberto.sassu@...wei.com>, Dmitry Kasatkin <dmitry.kasatkin@...il.com>, 
	Eric Snowberg <eric.snowberg@...cle.com>, Nicolas Schier <nicolas.schier@...ux.dev>, 
	Daniel Gomez <da.gomez@...nel.org>, Aaron Tomlin <atomlin@...mlin.com>, 
	"Christophe Leroy (CS GROUP)" <chleroy@...nel.org>, Nicolas Schier <nsc@...nel.org>, 
	Nicolas Bouchinet <nicolas.bouchinet@....cyber.gouv.fr>, Xiu Jianfeng <xiujianfeng@...wei.com>, 
	Fabian Grünbichler <f.gruenbichler@...xmox.com>, Arnout Engelen <arnout@...t.net>, 
	Mattia Rizzolo <mattia@...reri.org>, kpcyrd <kpcyrd@...hlinux.org>, 
	Christian Heusel <christian@...sel.eu>, Câju Mihai-Drosi <mcaju95@...il.com>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arch@...r.kernel.org, linux-modules@...r.kernel.org, 
	linux-security-module@...r.kernel.org, linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
	linux-integrity@...r.kernel.org
Subject: Re: [PATCH v4 13/17] module: Report signature type to users

On 2026-01-29 15:44:31+0100, Petr Pavlu wrote:
> On 1/13/26 1:28 PM, Thomas Weißschuh wrote:
> > The upcoming CONFIG_MODULE_HASHES will introduce a signature type.
> > This needs to be handled by callers differently than PKCS7 signatures.
> > 
> > Report the signature type to the caller and let them verify it.
> > 
> > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > ---
> > [...]
> > diff --git a/kernel/module/main.c b/kernel/module/main.c
> > index d65bc300a78c..2a28a0ece809 100644
> > --- a/kernel/module/main.c
> > +++ b/kernel/module/main.c
> > @@ -3348,19 +3348,24 @@ static int module_integrity_check(struct load_info *info, int flags)
> >  {
> >  	bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
> >  				       MODULE_INIT_IGNORE_VERMAGIC);
> > +	enum pkey_id_type sig_type;
> >  	size_t sig_len;
> >  	const u8 *sig;
> >  	int err = 0;
> >  
> >  	if (IS_ENABLED(CONFIG_MODULE_SIG_POLICY)) {
> >  		err = mod_split_sig(info->hdr, &info->len, mangled_module,
> > -				    &sig_len, &sig, "module");
> > +				    &sig_type, &sig_len, &sig, "module");
> >  		if (err)
> >  			return err;
> >  	}
> >  
> > -	if (IS_ENABLED(CONFIG_MODULE_SIG))
> > +	if (IS_ENABLED(CONFIG_MODULE_SIG) && sig_type == PKEY_ID_PKCS7) {
> >  		err = module_sig_check(info, sig, sig_len);
> > +	} else {
> > +		pr_err("module: not signed with expected PKCS#7 message\n");
> > +		err = -ENOPKG;
> > +	}
> 
> The new else branch means that if the user chooses not to configure any
> module integrity policy, they will no longer be able to load any
> modules. I think this entire if-else part should be moved under the
> IS_ENABLED(CONFIG_MODULE_SIG_POLICY) block above, as I'm mentioning on
> patch #12.

Ack.