CVE-2021-47439

In the Linux kernel, the following vulnerability has been resolved:

net: dsa: microchip: Added the condition for scheduling kszmibread_work

When the ksz module is installed and removed using rmmod, kernel crashes with null pointer dereferrence error. During rmmod, kszswitchremove function tries to cancel the mibreadworkqueue using canceldelayedwork_sync routine and unregister switch from dsa.

During dsaunregisterswitch it calls kszmaclinkdown, which in turn reschedules the workqueue since mibinterval is non-zero. Due to which queue executed after mibinterval and it tries to access dp->slave. But the slave is unregistered in the kszswitch_remove function. Hence kernel crashes.

To avoid this crash, before canceling the workqueue, resetted the mib_interval to 0.

v1 -> v2: -Removed the if condition in kszmibread_work