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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. Fixes: 9f5e8ee ("sh: generic push-switch framework.") Signed-off-by: Duoming Zhou <[email protected]> Reviewed-by: Geert Uytterhoeven <[email protected]> Reviewed-by: John Paul Adrian Glaubitz <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: John Paul Adrian Glaubitz <[email protected]>
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