Re: [Regression] cached max_state breaks ACPI processor cooling device

[Linux regression tracking #adding (Thorsten Leemhuis)]

[CCing the regression list, as it should be in the loop for regressions:
https://docs.kernel.org/admin-guide/reporting-regressions.html]

[TLDR: I'm adding this report to the list of tracked Linux kernel
regressions; the text you find below is based on a few templates
paragraphs you might have encountered already in similar form.
See link in footer if these mails annoy you.]

On 25.02.23 06:29, Zhang, Rui wrote:
>
> Starting from commit c408b3d1d9bb("thermal: Validate new state in
> cur_state_store()") and commit a365105c685c("thermal: sysfs: Reuse
> cdev->max_state"), the cdev->get_max_state() is evaluated only once
> during cooling device registration.
> 
> This is done to fix the below Smatch static checker warning:
> 	drivers/thermal/thermal_sysfs.c:656 thermal_cooling_device_stats_update()
> 	warn: potential integer overflow from user 'stats->state *
> stats->max_states + new_state'
> reported here https://lore.kernel.org/all/Y0ltRJRjO7AkawvE@kili/.
> 
> But this actually breaks cooling devices which could have dynamic max
> cooling state, like ACPI processor cooling device.

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot ^introduced c408b3d1d9bb
#regzbot title thermal: cached max_state breaks ACPI processor cooling
device
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply and tell me -- ideally
while also telling regzbot about it, as explained by the page listed in
the footer of this mail.

Developers: When fixing the issue, remember to add 'Link:' tags pointing
to the report (the parent of this mail). See page linked in footer for
details.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
That page also explains what to do if mails like this annoy you.