CVE-2023-52629

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

sh: push-switch: Reorder cleanup operations to avoid use-after-free bug

The original code puts flush_work() before timer_shutdown_sync()

in switch_drv_remove(). Although we use flush_work() to stop

the worker, it could be rescheduled in switch_timer(). As a result,

a use-after-free bug can occur. The details are shown below:

(cpu 0) | (cpu 1)

switch_drv_remove() |

flush_work() |

... | switch_timer // timer

| schedule_work(&psw->work)

timer_shutdown_sync() |

... | switch_work_handler // worker

kfree(psw) // free |

| psw->state = 0 // use

This patch puts timer_shutdown_sync() before flush_work() to

mitigate the bugs. As a result, the worker and timer will be

stopped safely before the deallocate operations.