Re: [PATCH] x86/mce: Improve mcheck_init_device() error handling.

Borislav Petkov
2014-04-28T19:36:58Z

On Fri, Apr 25, 2014 at 07:40:04PM +0200, Mathieu Souchaud wrote:
> Check return code of every function called.
>
> Signed-off-by: Mathieu Souchaud <mattieu.souchaud@free.fr>
> ---
> arch/x86/kernel/cpu/mcheck/mce.c | 30 +++++++++++++++++++++++-------
> 1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 68317c8..b865285 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -2437,33 +2437,49 @@ static __init int mcheck_init_device(void)
> int err;
> int i = 0;
>
> - if (!mce_available(&boot_cpu_data))
> - return -EIO;
> + if (!mce_available(&boot_cpu_data)) {
> + err = -EIO;
> + goto err_out;
> + }
>
> - zalloc_cpumask_var(&mce_device_initialized, GFP_KERNEL);
> + if (!zalloc_cpumask_var(&mce_device_initialized, GFP_KERNEL)) {
> + err = -ENOMEM;
> + goto err_out;
> + }
>
> mce_init_banks();
>
> err = subsys_system_register(&mce_subsys, NULL);
> if (err)
> - return err;
> + goto err_out_mem;
>
> cpu_notifier_register_begin();
> for_each_online_cpu(i) {
> err = mce_device_create(i);
> if (err) {
> cpu_notifier_register_done();
> - return err;
> + goto err_out_mem;

Actually, this should partially unwind what has been created already,
like this:

if (err)
goto err_device_create;

and then at that label, you can do:

err_device_create:
while (--i > 0)
mce_device_remove(i);
cpu_notifier_register_done();

And then here come your other labels:

err_out_mem:
....

And so on. Makes sense?

> register_syscore_ops(&mce_syscore_ops);
> - __register_hotcpu_notifier(&mce_cpu_notifier);
> + err = __register_hotcpu_notifier(&mce_cpu_notifier);
> cpu_notifier_register_done();
> + if (err)
> + goto err_out_mem;

This needs to be a label which goes before err_device_create above and
which does

err_reg_hotcpu:
unregister_syscore_ops(&mce_syscore_ops);

>
> /* register character device /dev/mcelog */
> - misc_register(&mce_chrdev_device);
> + err = misc_register(&mce_chrdev_device);
> + if (err)
> + goto err_out_mem;

And this has to go to the top-label which unwinds all the work, along
with the mce percpu devices like:

for_each_online_cpu(i)
mce_device_remove(i);

unregister_hotcpu_notifier(&mce_cpu_notifier);

...

and so on.

Ok, am I making sense?

Don't be afraid to give it a try, even if it is wrong - we'll get it
right eventually :-)

For testing, you can use a kvm guest and "inject" errors in the
registration code just to see whether it works as expected.

And feel free to ask questions if something's not clear.

Thanks!

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
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