Messages in this thread | | | Date | Tue, 23 Aug 2022 10:26:59 +0800 | Subject | Re: [REGRESSION 5.19] NULL dereference by ucsi_acpi driver | From | Linyu Yuan <> |
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On 8/22/2022 9:24 PM, Heikki Krogerus wrote: > Hi, > > On Sat, Aug 20, 2022 at 08:40:52PM +0200, Greg Kroah-Hartman wrote: >> On Fri, Aug 19, 2022 at 06:32:43PM +0200, Takashi Iwai wrote: >>> Hi, >>> >>> we've got multiple reports about 5.19 kernel starting crashing after >>> some time, and this turned out to be triggered by ucsi_acpi driver. >>> The details are found in: >>> https://bugzilla.suse.com/show_bug.cgi?id=1202386 >>> >>> The culprit seems to be the commit 87d0e2f41b8c >>> usb: typec: ucsi: add a common function ucsi_unregister_connectors() >> Adding Heikki to the thread... >> >>> >>> This commit looks as if it were a harmless cleanup, but this failed in >>> a subtle way. Namely, in the error scenario, the driver gets an error >>> at ucsi_register_altmodes(), and goes to the error handling to release >>> the resources. Through this refactoring, the release part was unified >>> to a funciton ucsi_unregister_connectors(). And there, it has a NULL >>> check of con->wq, and it bails out the loop if it's NULL. >>> Meanwhile, ucsi_register_port() itself still calls destroy_workqueue() >>> and clear con->wq at its error path. This ended up in the leftover >>> power supply device with the uninitialized / cleared device. >>> >>> It was confirmed that the problem could be avoided by a simple >>> revert. >> I'll be glad to revert this now, unless Heikki thinks: >> >>> I guess another fix could be removing the part clearing con->wq, i.e. >>> >>> --- a/drivers/usb/typec/ucsi/ucsi.c >>> +++ b/drivers/usb/typec/ucsi/ucsi.c >>> @@ -1192,11 +1192,6 @@ static int ucsi_register_port(struct ucsi *ucsi, int index) >>> out_unlock: >>> mutex_unlock(&con->lock); >>> >>> - if (ret && con->wq) { >>> - destroy_workqueue(con->wq); >>> - con->wq = NULL; >>> - } >>> - >>> return ret; >>> } >>> >>> >>> ... but it's totally untested and I'm not entirely sure whether it's >>> better. >> that is any better? > No, I don't think that's better. Right now I would prefer that we play > it safe and revert. > > The conditions are different in the two places where the ports are > unregistered in this driver. Therefore I don't think it makes sense > to use a function like ucsi_unregister_connectors() that tries to > cover both cases. It will always be a little bit fragile. > > Instead we could introduce a function that can be used to remove a > single port. That would leave the handling of the conditions to the > callers of the function, but it would still remove the boilerplate. > That would be much safer IMO. > > But to fix this problem, I think we should revert.
but revert will happen on several stable branch, right ?
i think simple fix is good, from my view there is no big differences to create a function for a single port.
> > thanks, >
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