enic: fix tx_hang_reset use-after-free on device removal

In the Linux kernel, the following vulnerability has been resolved: enic: fix tx_hang_reset use-after-free on device removal enic_remove() cancels the reset and change_mtu_work items but does not cancel tx_hang_reset. A TX timeout that fires while the device is being removed can schedule enic_tx_hang_reset() so that it runs after free_netdev(), resulting in a use-after-free. cancel_work_sync() alone is not sufficient here: the still-live watchdog and notify paths can re-schedule these work items in the window between the cancel and unregister_netdev(). Use disable_work_sync(), which cancels the work and blocks any subsequent schedule_work() from requeuing it, and apply it to the reset and change_mtu_work items as well so the same requeue race is closed for all teardown work.

Where it's fixed