Messages in this thread | | | Date | Fri, 8 Oct 2021 11:34:02 -0700 | From | Jakub Kicinski <> | Subject | Re: [PATCH net] net: dsa: microchip: Added the condition for scheduling ksz_mib_read_work |
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On Fri, 8 Oct 2021 15:58:16 +0200 Andrew Lunn wrote: > On Fri, Oct 08, 2021 at 02:13:48PM +0530, Arun Ramadoss wrote: > > When the ksz module is installed and removed using rmmod, kernel crashes > > with null pointer dereferrence error. During rmmod, ksz_switch_remove > > function tries to cancel the mib_read_workqueue using > > cancel_delayed_work_sync routine. > > > > At the end of mib_read_workqueue execution, it again reschedule the > > workqueue unconditionally. Due to which queue rescheduled after > > mib_interval, during this execution it tries to access dp->slave. But > > the slave is unregistered in the ksz_switch_remove function. Hence > > kernel crashes. > > Something not correct here. > > https://www.kernel.org/doc/html/latest/core-api/workqueue.html?highlight=delayed_work#c.cancel_delayed_work_sync > > This is cancel_work_sync() for delayed works. > > and > > https://www.kernel.org/doc/html/latest/core-api/workqueue.html?highlight=delayed_work#c.cancel_work_sync > > This function can be used even if the work re-queues itself or > migrates to another workqueue. > > Maybe the real problem is a missing call to destroy_worker()?
Also the cancel_delayed_work_sync() is suspiciously early in the remove flow. There is a schedule_work call in ksz_mac_link_down() which may schedule the work back in. That'd also explain why the patch helps since ksz_mac_link_down() only schedules if (dev->mib_read_interval).
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