Re: [PATCH 1/1] kernel/module.c: wakeup processes in module_wq on module unload

[Jessica Yu]

+++ Konstantin Khorenko [13/11/19 12:29 +0300]:
> Fix the race between load and unload a kernel module.
>
> sys_delete_module()
> try_stop_module()
>  mod->state = _GOING
> 					add_unformed_module()
> 					 old = find_module_all()
> 					 (old->state == _GOING =>
> 					  wait_event_interruptible())
>
> 					 During pre-condition
> 					 finished_loading() rets 0
> 					 schedule()
> 					 (never gets waken up later)
> free_module()
>  mod->state = _UNFORMED
>   list_del_rcu(&mod->list)
>   (dels mod from "modules" list)
>
> return
>
> The race above leads to modprobe hanging forever on loading
> a module.
>
> Error paths on loading module call wake_up_all(&module_wq) after
> freeing module, so let's do the same on straight module unload.
>
> Fixes: 6e6de3dee51a ("kernel/module.c: Only return -EEXIST
> for modules that have finished loading")
>
> Signed-off-by: Konstantin Khorenko <khorenko@xxxxxxxxxxxxx>

Thanks Konstantin for catching this. I've applied this to
modules-next.

Jessica