Re: [PATCH RESEND] power: supply: avoid nullptr deref in __power_supply_is_system_supplied

[Mark Pearson <markpearson@lenovo.com>]

<Note - hope this works - moved to my more opensource friendly email
account>

On 2022-09-12 08:20, Mark Pearson wrote:
> 
> --------------------------------------------------------------------------------
> *From:* Jason A. Donenfeld <Jason@zx2c4.com>
> *Sent:* September 12, 2022 6:56
> *To:* Sebastian Reichel <sebastian.reichel@collabora.com>; Mark Pearson 
> <mpearson@lenovo.com>
> *Cc:* linux-pm@vger.kernel.org <linux-pm@vger.kernel.org>; 
> stable@vger.kernel.org <stable@vger.kernel.org>; Rafael J . Wysocki 
> <rafael@kernel.org>
> *Subject:* [External] Re: [PATCH RESEND] power: supply: avoid nullptr deref in 
> __power_supply_is_system_supplied
> CC+ Mark Pearson from Lenovo
> Full thread is here:
> https://lore.kernel.org/all/YwDsy3ZUgTtlKH9r@zx2c4.com/ <https://lore.kernel.org/all/YwDsy3ZUgTtlKH9r@zx2c4.com/>> 
> On Mon, Sep 12, 2022 at 11:48 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>>
>> Ah another thing:
>>
>> On Mon, Sep 12, 2022 at 11:45 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>> > My machine went through three changes I know about between the threshold
>> > of "not crashing" and "crashing":
>> > - Upgraded to 5.19 and then 6.0-rc1.
>> > - I used my laptop on batteries for a prolonged period of time for the
>> >   first time in a while.
>> > - I updated KDE, whose power management UI elements may or may not make
>> >   frequent calls to this subsystem to update some visual representation.
>>
>> - Updated my BIOS.
> 
> GASP! The plot thickens.
> 
> It appears that the BIOS update I applied has been removed from
> https://pcsupport.lenovo.com/fr/en/downloads/ds551052-bios-update-utility-bootable-cd-for-windows-10-64-bit-and-linux-thinkpad-p1-gen-4-x1-extreme-gen-4 <https://pcsupport.lenovo.com/fr/en/downloads/ds551052-bios-update-utility-bootable-cd-for-windows-10-64-bit-and-linux-thinkpad-p1-gen-4-x1-extreme-gen-4>
> and now it only shows the 1.16 version. I updated from 1.16 to 1.18.
> 
> The missing release notes are still online if you futz with the URL:
> https://download.lenovo.com/pccbbs/mobiles/n40ur14w.txt 
> <https://download.lenovo.com/pccbbs/mobiles/n40ur14w.txt>
> https://download.lenovo.com/pccbbs/mobiles/n40ur15w.txt 
> <https://download.lenovo.com/pccbbs/mobiles/n40ur15w.txt>
> 
> One of the items for 1.17 says:
>> - (Fix) Fixed an issue where it took a long time to update the battery FW.
> 
> So maybe something was happening here...
> 
> I'm CC'ing Mark from Lenovo to see if he has any insight as to why
> this BIOS update was pulled.
> 
> Maybe the battery was appearing and disappearing rapidly. If that's
> correct, then it'd indicate that this bandaid patch is *wrong* and
> what actually is needed is some kind of reference counting or RCU
> around that sysfs interface (and maybe others).
> 
> Jason

Hi Jason,

I'll have to check with the FW team but looking at the internal notes I
think the FW was pulled because of a graphics display regression.
Version 36W was fixing a brightness control issue in discrete mode and
37W (not yet released) is fixing external display - so my guess is
something about the fix in 36W has a side effect

More interesting is the EC FW updates. There isn't a new version posted
but there are fixes in the previous version (EC 33W) for a fix for a
'suspected EC-Battery communication transaction failure'. Is that
potentially related to this patch in some way? I can go and ask for more
details if we think it's related. I'll also see if I can repro on my
P1G4 - but I hadn't seen any other reports so it might be HW specific.

Can you confirm which FW you have from the BIOS setup screen (F1 during
early boot)? BIOS and EC please.

Mark