linux-kernel - Re: Unloaded tainted modules list with tcrypt

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Date:   Mon, 10 Oct 2022 23:25:54 +0100
From:   Aaron Tomlin <atomlin@...hat.com>
To:     "Elliott, Robert (Servers)" <elliott@....com>
Cc:     "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Unloaded tainted modules list with tcrypt

On Mon 2022-10-10 15:12 +0000, Elliott, Robert (Servers) wrote:
> When repeatedly using the tcrypt module (which is designed to never
> load successfully), the "Unloaded tainted modules" list grows forever:
> 
> Unloaded tainted modules: tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 tcrypt():1 
> tcrypt():1 tcrypt():1 padlock_aes():1 padlock_aes():1 
> isst_if_mbox_msr():1 acpi_cpufreq():1 pcc_cpufreq():1 isst_if_mbox_msr():1 
> acpi_cpufreq():1 pcc_cpufreq():1 acpi_cpufreq():1 acpi_cpufreq():1 
> pcc_cpufreq():1 isst_if_mbox_msr():1 acpi_cpufreq():1 acpi_cpufreq():1 
> pcc_cpufreq():1 isst_if_mbox_msr():1 acpi_cpufreq():1 acpi_cpufreq():1 
> isst_if_mbox_msr():1 isst_if_mbox_msr():1 
> acpi_cpufreq():1 pcc_cpufreq():1 acpi_cpufreq():1 isst_if_mbox_msr():1
> 
> Some other modules like acpi_cpufreq() are repeated too.
> 
> Maybe this check after the name comparison:
> 	mod_taint->taints & mod->taints
> should be:
> 	mod_taint->taints == mod->taints
> 
> or shouldn't be there at all?
> 

Hi Elliot,

Sorry about that.

This is already addressed in linux-next:

commit a0830747f4e6810876e5f5329ce941e258e13a22
Author: Aaron Tomlin <atomlin@...hat.com>
Date:   Fri Oct 7 14:32:44 2022 +0100

    module: tracking: Keep a record of tainted unloaded modules only
    
    This patch ensures that no module record/or entry is added to the
    unloaded_tainted_modules list if it does not carry a taint.
    
    Reported-by: Alexey Dobriyan <adobriyan@...il.com>
    Fixes: 99bd9956551b ("module: Introduce module unload taint tracking")
    
    Signed-off-by: Aaron Tomlin <atomlin@...hat.com>

diff --git a/kernel/module/tracking.c b/kernel/module/tracking.c
index a139e63b6f20..26d812e07615 100644
--- a/kernel/module/tracking.c
+++ b/kernel/module/tracking.c
@@ -22,6 +22,9 @@ int try_add_tainted_module(struct module *mod)
 
 	module_assert_mutex_or_preempt();
 
+	if (!mod->taints)
+		goto out;
+
 	list_for_each_entry_rcu(mod_taint, &unloaded_tainted_modules, list,
 				lockdep_is_held(&module_mutex)) {
 		if (!strcmp(mod_taint->name, mod->name) &&




Kind regards,

-- 
Aaron Tomlin