Re: edac KASAN warning in experimental arm64 allmodconfig boot

[John Garry]

On 14/10/2019 17:15, James Morse wrote:
> Hi John,

Hi James,

> On 14/10/2019 16:18, John Garry wrote:
> > I'm experimenting by trying to boot an allmodconfig arm64 kernel, as mentioned here:
>
> Crumbs!
>
>
> > One thing that I noticed - it's hard to miss actually - is the amount of complaining from
> > KASAN about the EDAC/ghes code. Maybe this is something I should not care about/red
> > herring, or maybe something genuine. Let me know what you think.
>
> Hmmm, I thought I tested this recently...
>
> > Log snippet (I cut off after the first KASAN warning):
> >
> > [   70.471011][    T1] random: get_random_u32 called from new_slab+0x360/0x698 with
> > crng_init=0
>
> > [   70.478671][    T1] [Firmware Bug]: APEI: Invalid bit width + offset in GAR
> > [0x94110034/64/0/3/0]
>
> (this one's for you right?)

Yeah, I'll report it. It might be already fixed.

> > [   70.700412][    T1] ------------[ cut here ]------------
>
> > [   70.802080][    T1] Call trace:
> > [   70.802093][    T1]  debug_print_object+0xec/0x130
> > [   70.802106][    T1]  __debug_check_no_obj_freed+0x114/0x290
> > [   70.802119][    T1]  debug_check_no_obj_freed+0x18/0x28
> > [   70.802130][    T1]  slab_free_freelist_hook+0x18c/0x228
> > [   70.802140][    T1]  kfree+0x264/0x420
> > [   70.802157][    T1]  _edac_mc_free+0x6c/0x210
> > [   70.814163][    T1]  edac_mc_free+0x68/0x88
> > [   70.814177][    T1]  ghes_edac_unregister+0x44/0x70
> > [   70.814193][    T1]  ghes_remove+0x274/0x2a0
>
> Ugh. This must be the test driver remove thing.

Yeah, the probe, remove, probe again flow from 
CONFIG_DEBUG_TEST_DRIVER_REMOVE.

> I've reproduced this, but had to remove the parent GHES twice. It looks like it tries to
> use the first ghes_edac global variables when freeing the second. ghes_init prevents it
> from re-allocating over the top.
>
> The below diff fixes it for me.

And for me by the looks of it. That's with CONFIG_DEBUG_KOBJECT_RELEASE 
now unset, but I expect the same with it set.

(I'll post it as a proper patch once I've done the
> archaeology)
>
> -----------%<-----------
> diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c
> index d413a0bdc9ad..955b59b6aade 100644
> --- a/drivers/edac/ghes_edac.c
> +++ b/drivers/edac/ghes_edac.c
> @@ -554,6 +554,7 @@ void ghes_edac_unregister(struct ghes *ghes)
>                 return;
>
>         mci = ghes_pvt->mci;
> +       ghes_pvt = NULL;
>         edac_mc_del_mc(mci->pdev);
>         edac_mc_free(mci);
>  }
>
> -----------%<-----------

Thanks,
John

BTW, I am not sure if my response to Boris was rejected due to 
attachments, as but it is here:

https://lore.kernel.org/linux-edac/dc974549-6ea4-899d-7f3a-b2fcfafe1528@xxxxxxx/T/#ma0e122ca0eda9d80e869af179352f75037146d3c

> Thanks!
>
> James
>
> .