On Thu, Jul 16, 2020 at 10:38:00AM -0700, Guenter Roeck wrote: > On Thu, Jul 16, 2020 at 10:28 AM Jarkko Sakkinen > <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > > > On Tue, Jul 14, 2020 at 08:48:38AM -0700, Guenter Roeck wrote: > > > On Tue, Jul 14, 2020 at 4:32 AM Jarkko Sakkinen > > > <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > > > > > > > On Fri, Jul 10, 2020 at 11:25:44AM -0700, Andrey Pronin wrote: > > > > > > Why does not tpm_del_char_device need this? > > > > > > > > > > "Not" is a typo in the sentence above, right? tpm_del_char_device *does* > > > > > need the fix. When tpm_class_shutdown is called it sets chip->ops to > > > > > NULL. If tpm_del_char_device is called after that, it doesn't check if > > > > > chip->ops is NULL (normal kernel API and char device API calls go > > > > > through tpm_try_get_ops, but tpm_del_char_device doesn't) and proceeds to > > > > > call tpm2_shutdown(), which tries sending the command and dereferences > > > > > chip->ops. > > > > > > > > It's a typo, yes. Sorry about that. > > > > > > > > tpm_class_shutdown() is essentially tail of tpm_del_char_device(). > > > > > > > > To clean things up, I'd suggest dropping tpm_del_char_device() and > > > > call tpm_class_shutdown() in tpm_chip_unregisters() along, and open > > > > coding things that prepend it in tpm_del_char_device(). > > > > > > > > > > Personally I would have preferred two separate patches, one to fix the > > > immediate problem (with Cc: stable) and one for the cleanup, but I > > > guess merging both into one is ok as long as it is marked for stable. > > > > > > Thanks, > > > Guenter > > > > Not sure about stable as this issue does not afaik concern earlier > > kernel versions? > > > > I just had a quick look into linux-5.4.y, and it seemed to me that it > is affected. Maybe I am wrong. Either case, we already applied this > patch to all affected ChromeOS kernel branches, so from our > perspective it doesn't really matter. > > Thanks, > Guenter I'm fine with cc'ing stable after consideration given the benefits. Given that conclusion, it is better to break this down to two part series as you proposed. /Jarkko
