linux-kernel - Re: [PATCH 1/1] kernel/module.c: wakeup processes in module

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Date:   Fri, 15 Nov 2019 11:28:33 +0100
From:   Jessica Yu <jeyu@...nel.org>
To:     Konstantin Khorenko <khorenko@...tuozzo.com>
Cc:     Prarit Bhargava <prarit@...hat.com>,
        Barret Rhoden <brho@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        linux-kernel@...r.kernel.org, David Arcari <darcari@...hat.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 1/1] kernel/module.c: wakeup processes in module_wq on
 module unload

+++ 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@...tuozzo.com>

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

Jessica