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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2c27c9cf-0ce3-1c7f-bdc2-760d6d37d4d1@redhat.com>
Date:   Mon, 15 Apr 2019 08:04:05 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     linux-kernel@...r.kernel.org, cavery@...hat.com
Subject: Re: [PATCH] modules: Only return -EEXIST for modules that have
 finished loading



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@...hat.com>
>> Reported-by: Cathy Avery <cavery@...hat.com>
>> Cc: Jessica Yu <jeyu@...nel.org>
> 
> Applied to modules-next. Thanks Prarit!

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

Thanks,

P.

> 
> Jessica
>