Re: [REGRESSION 5.19] NULL dereference by ucsi_acpi driver

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 8/21/2022 2:40 AM, 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.

this part is original code, yes, but when I make the change you mentioned,

as in the function ucsi_unregister_connectors(),  just use con->wq to represent which connector initialized previous,

indeed if we clear it in ucsi_register_port(), something will left unclear.

please send a patch to fix it.

I think your change is good.

that is any better?

thanks,

greg k-h



[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux