[PATCH] modules: Only return -EEXIST for modules that have finished loading

[PATCH] modules: Only return -EEXIST for modules that have finished loading

[Prarit Bhargava]

Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
linux guests boot with repeated errors:

amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)

The warnings occur because the module code erroneously returns -EEXIST
for modules that have failed to load and are in the process of being
removed from the module list.

module amd64_edac_mod has a dependency on module edac_mce_amd.  Using
modules.dep, systemd will load edac_mce_amd for every request of
amd64_edac_mod.  When the edac_mce_amd module loads, the module has
state MODULE_STATE_UNFORMED and once the module load fails and the state
becomes MODULE_STATE_GOING.  Another request for edac_mce_amd module
executes and add_unformed_module() will erroneously return -EEXIST even
though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
fails because of unknown symbols from edac_mce_amd.

add_unformed_module() must wait to return for any case other than
MODULE_STATE_LIVE to prevent a race between multiple loads of
dependent modules.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Reported-by: Cathy Avery <cavery@redhat.com>
Cc: Jessica Yu <jeyu@kernel.org>
---
 kernel/module.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 0b9aa8ab89f0..e8c1de2ab4e1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3566,8 +3566,7 @@ static int add_unformed_module(struct module *mod)
 	mutex_lock(&module_mutex);
 	old = find_module_all(mod->name, strlen(mod->name), true);
 	if (old != NULL) {
-		if (old->state == MODULE_STATE_COMING
-		    || old->state == MODULE_STATE_UNFORMED) {
+		if (old->state != MODULE_STATE_LIVE) {
 			/* Wait in case it fails to load. */
 			mutex_unlock(&module_mutex);
 			err = wait_event_interruptible(module_wq,
-- 
2.17.2

Re: [PATCH] modules: Only return -EEXIST for modules that have finished loading

[Prarit Bhargava]

Jessica?  ping?

P.

On 4/2/19 9:39 AM, Prarit Bhargava wrote:
> Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
> linux guests boot with repeated errors:
> 
> amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
> amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
> amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
> amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
> amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
> amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
> 
> The warnings occur because the module code erroneously returns -EEXIST
> for modules that have failed to load and are in the process of being
> removed from the module list.
> 
> module amd64_edac_mod has a dependency on module edac_mce_amd.  Using
> modules.dep, systemd will load edac_mce_amd for every request of
> amd64_edac_mod.  When the edac_mce_amd module loads, the module has
> state MODULE_STATE_UNFORMED and once the module load fails and the state
> becomes MODULE_STATE_GOING.  Another request for edac_mce_amd module
> executes and add_unformed_module() will erroneously return -EEXIST even
> though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
> Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
> fails because of unknown symbols from edac_mce_amd.
> 
> add_unformed_module() must wait to return for any case other than
> MODULE_STATE_LIVE to prevent a race between multiple loads of
> dependent modules.
> 
> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> Reported-by: Cathy Avery <cavery@redhat.com>
> Cc: Jessica Yu <jeyu@kernel.org>
> ---
>  kernel/module.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 0b9aa8ab89f0..e8c1de2ab4e1 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3566,8 +3566,7 @@ static int add_unformed_module(struct module *mod)
>  	mutex_lock(&module_mutex);
>  	old = find_module_all(mod->name, strlen(mod->name), true);
>  	if (old != NULL) {
> -		if (old->state == MODULE_STATE_COMING
> -		    || old->state == MODULE_STATE_UNFORMED) {
> +		if (old->state != MODULE_STATE_LIVE) {
>  			/* Wait in case it fails to load. */
>  			mutex_unlock(&module_mutex);
>  			err = wait_event_interruptible(module_wq,
> 

Re: [PATCH] modules: Only return -EEXIST for modules that have finished loading

[Jessica Yu]

+++ Prarit Bhargava [02/04/19 09:39 -0400]:
>Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
>linux guests boot with repeated errors:
>
>amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>
>The warnings occur because the module code erroneously returns -EEXIST
>for modules that have failed to load and are in the process of being
>removed from the module list.
>
>module amd64_edac_mod has a dependency on module edac_mce_amd.  Using
>modules.dep, systemd will load edac_mce_amd for every request of
>amd64_edac_mod.  When the edac_mce_amd module loads, the module has
>state MODULE_STATE_UNFORMED and once the module load fails and the state
>becomes MODULE_STATE_GOING.  Another request for edac_mce_amd module
>executes and add_unformed_module() will erroneously return -EEXIST even
>though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
>Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
>fails because of unknown symbols from edac_mce_amd.
>
>add_unformed_module() must wait to return for any case other than
>MODULE_STATE_LIVE to prevent a race between multiple loads of
>dependent modules.
>
>Signed-off-by: Prarit Bhargava <prarit@redhat.com>
>Reported-by: Cathy Avery <cavery@redhat.com>
>Cc: Jessica Yu <jeyu@kernel.org>

Applied to modules-next. Thanks Prarit!

Jessica

Re: [PATCH] modules: Only return -EEXIST for modules that have finished loading

[Prarit Bhargava]

On 4/15/19 7:23 AM, Jessica Yu wrote:
> +++ Prarit Bhargava [02/04/19 09:39 -0400]:
>> Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
>> linux guests boot with repeated errors:
>>
>> amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>> amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>> amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>> amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>> amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>> amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>>
>> The warnings occur because the module code erroneously returns -EEXIST
>> for modules that have failed to load and are in the process of being
>> removed from the module list.
>>
>> module amd64_edac_mod has a dependency on module edac_mce_amd.  Using
>> modules.dep, systemd will load edac_mce_amd for every request of
>> amd64_edac_mod.  When the edac_mce_amd module loads, the module has
>> state MODULE_STATE_UNFORMED and once the module load fails and the state
>> becomes MODULE_STATE_GOING.  Another request for edac_mce_amd module
>> executes and add_unformed_module() will erroneously return -EEXIST even
>> though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
>> Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
>> fails because of unknown symbols from edac_mce_amd.
>>
>> add_unformed_module() must wait to return for any case other than
>> MODULE_STATE_LIVE to prevent a race between multiple loads of
>> dependent modules.
>>
>> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
>> Reported-by: Cathy Avery <cavery@redhat.com>
>> Cc: Jessica Yu <jeyu@kernel.org>
> 
> Applied to modules-next. Thanks Prarit!

Jessica, could I have the URL of the git tree?

Thanks,

P.

> 
> Jessica
> 

Re: [PATCH] modules: Only return -EEXIST for modules that have finished loading

[Jessica Yu]

+++ Prarit Bhargava [15/04/19 08:04 -0400]:
>
>
>On 4/15/19 7:23 AM, Jessica Yu wrote:
>> +++ Prarit Bhargava [02/04/19 09:39 -0400]:
>>> Microsoft HyperV disables the X86_FEATURE_SMCA bit on AMD systems, and
>>> linux guests boot with repeated errors:
>>>
>>> amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>>> amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>>> amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>>> amd64_edac_mod: Unknown symbol amd_unregister_ecc_decoder (err -2)
>>> amd64_edac_mod: Unknown symbol amd_register_ecc_decoder (err -2)
>>> amd64_edac_mod: Unknown symbol amd_report_gart_errors (err -2)
>>>
>>> The warnings occur because the module code erroneously returns -EEXIST
>>> for modules that have failed to load and are in the process of being
>>> removed from the module list.
>>>
>>> module amd64_edac_mod has a dependency on module edac_mce_amd.  Using
>>> modules.dep, systemd will load edac_mce_amd for every request of
>>> amd64_edac_mod.  When the edac_mce_amd module loads, the module has
>>> state MODULE_STATE_UNFORMED and once the module load fails and the state
>>> becomes MODULE_STATE_GOING.  Another request for edac_mce_amd module
>>> executes and add_unformed_module() will erroneously return -EEXIST even
>>> though the previous instance of edac_mce_amd has MODULE_STATE_GOING.
>>> Upon receiving -EEXIST, systemd attempts to load amd64_edac_mod, which
>>> fails because of unknown symbols from edac_mce_amd.
>>>
>>> add_unformed_module() must wait to return for any case other than
>>> MODULE_STATE_LIVE to prevent a race between multiple loads of
>>> dependent modules.
>>>
>>> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
>>> Reported-by: Cathy Avery <cavery@redhat.com>
>>> Cc: Jessica Yu <jeyu@kernel.org>
>>
>> Applied to modules-next. Thanks Prarit!
>
>Jessica, could I have the URL of the git tree?

Sure, you can find the modules-next branch at:

    git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux.git

Thanks,

Jessica