linux-kernel - Re: [PATCH v4 12/17] module: Move signature splitting up

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Message-ID: <aa92ce4a-d336-4d03-b87d-1c39b1c553da@suse.com>
Date: Thu, 29 Jan 2026 15:41:43 +0100
From: Petr Pavlu <petr.pavlu@...e.com>
To: Thomas Weißschuh <linux@...ssschuh.net>
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>,
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 Madhavan Srinivasan <maddy@...ux.ibm.com>,
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 Roberto Sassu <roberto.sassu@...wei.com>,
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Subject: Re: [PATCH v4 12/17] module: Move signature splitting up

On 1/13/26 1:28 PM, Thomas Weißschuh wrote:
> The signature splitting will also be used by CONFIG_MODULE_HASHES.
> 
> Move it up the callchain, so the result can be reused.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
> [...]
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index c09b25c0166a..d65bc300a78c 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -3346,10 +3346,21 @@ static int early_mod_check(struct load_info *info, int flags)
>  
>  static int module_integrity_check(struct load_info *info, int flags)
>  {
> +	bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
> +				       MODULE_INIT_IGNORE_VERMAGIC);
> +	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");
> +		if (err)
> +			return err;
> +	}
> +
>  	if (IS_ENABLED(CONFIG_MODULE_SIG))
> -		err = module_sig_check(info, flags);
> +		err = module_sig_check(info, sig, sig_len);
>  
>  	if (err)
>  		return err;

I suggest moving the IS_ENABLED(CONFIG_MODULE_SIG) block under the
new IS_ENABLED(CONFIG_MODULE_SIG_POLICY) section. I realize that
CONFIG_MODULE_SIG implies CONFIG_MODULE_SIG_POLICY, but I believe this
change makes it more apparent that this it the case. Otherwise, one
might for example wonder if sig_len in the module_sig_check() call can
be undefined.

	if (IS_ENABLED(CONFIG_MODULE_SIG_POLICY)) {
		err = mod_split_sig(info->hdr, &info->len, mangled_module,
				    &sig_len, &sig, "module");
		if (err)
			return err;

		if (IS_ENABLED(CONFIG_MODULE_SIG))
			err = module_sig_check(info, sig, sig_len);
	}

-- 
Thanks,
Petr