netdev - Re: [PATCH v3] mwifiex: fix sleep in atomic context bugs caused by dev

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Date:   Tue, 24 May 2022 10:08:39 +0800 (GMT+08:00)
From:   duoming@....edu.cn
To:     "Kalle Valo" <kvalo@...nel.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-wireless@...r.kernel.org, amitkarwar@...il.com,
        ganapathi017@...il.com, sharvari.harisangam@....com,
        huxinming820@...il.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        rafael@...nel.org
Subject: Re: [PATCH v3] mwifiex: fix sleep in atomic context bugs caused by
 dev_coredumpv


Hello,

On Mon, 23 May 2022 19:31:35 +0300 Kalle Valo wrote:

> >> > There are sleep in atomic context bugs when uploading device dump
> >> > data in mwifiex. The root cause is that dev_coredumpv could not
> >> > be used in atomic contexts, because it calls dev_set_name which
> >> > include operations that may sleep. The call tree shows execution
> >> > paths that could lead to bugs:
> >> >
> >> >    (Interrupt context)
> >> > fw_dump_timer_fn
> >> >   mwifiex_upload_device_dump
> >> >     dev_coredumpv(..., GFP_KERNEL)
> >> >       dev_coredumpm()
> >> >         kzalloc(sizeof(*devcd), gfp); //may sleep
> >> >         dev_set_name
> >> >           kobject_set_name_vargs
> >> >             kvasprintf_const(GFP_KERNEL, ...); //may sleep
> >> >             kstrdup(s, GFP_KERNEL); //may sleep
> >> >
> >> > In order to let dev_coredumpv support atomic contexts, this patch
> >> > changes the gfp_t parameter of kvasprintf_const and kstrdup in
> >> > kobject_set_name_vargs from GFP_KERNEL to GFP_ATOMIC. What's more,
> >> > In order to mitigate bug, this patch changes the gfp_t parameter
> >> > of dev_coredumpv from GFP_KERNEL to GFP_ATOMIC.
> >> 
> >> vmalloc in atomic context?
> >> 
> >> Not only does dev_coredumpm set a device name dev_coredumpm creates an
> >> entire device to hold the device dump.
> >> 
> >> My sense is that either dev_coredumpm needs to be rebuilt on a
> >> completely different principle that does not need a device to hold the
> >> coredump (so that it can be called from interrupt context) or that
> >> dev_coredumpm should never be called in an context that can not sleep.
> >
> > The following solution removes the gfp_t parameter of dev_coredumpv(), 
> > dev_coredumpm() and dev_coredumpsg() and change the gfp_t parameter of 
> > kzalloc() in dev_coredumpm() to GFP_KERNEL, in order to show that these 
> > functions can not be used in atomic context.
> >
> > What's more, I move the operations that may sleep into a work item and use
> > schedule_work() to call a kernel thread to do the operations that may sleep.
> >
> 
> [...]
> 
> > --- a/drivers/net/wireless/marvell/mwifiex/init.c
> > +++ b/drivers/net/wireless/marvell/mwifiex/init.c
> > @@ -63,11 +63,19 @@ static void wakeup_timer_fn(struct timer_list *t)
> >  		adapter->if_ops.card_reset(adapter);
> >  }
> >  
> > +static void fw_dump_work(struct work_struct *work)
> > +{
> > +	struct mwifiex_adapter *adapter =
> > +		container_of(work, struct mwifiex_adapter, devdump_work);
> > +
> > +	mwifiex_upload_device_dump(adapter);
> > +}
> > +
> >  static void fw_dump_timer_fn(struct timer_list *t)
> >  {
> >  	struct mwifiex_adapter *adapter = from_timer(adapter, t, devdump_timer);
> >  
> > -	mwifiex_upload_device_dump(adapter);
> > +	schedule_work(&adapter->devdump_work);
> >  }
> >  
> >  /*
> > @@ -321,6 +329,7 @@ static void mwifiex_init_adapter(struct mwifiex_adapter *adapter)
> >  	adapter->active_scan_triggered = false;
> >  	timer_setup(&adapter->wakeup_timer, wakeup_timer_fn, 0);
> >  	adapter->devdump_len = 0;
> > +	INIT_WORK(&adapter->devdump_work, fw_dump_work);
> >  	timer_setup(&adapter->devdump_timer, fw_dump_timer_fn, 0);
> >  }
> >  
> > @@ -401,6 +410,7 @@ mwifiex_adapter_cleanup(struct mwifiex_adapter *adapter)
> >  {
> >  	del_timer(&adapter->wakeup_timer);
> >  	del_timer_sync(&adapter->devdump_timer);
> > +	cancel_work_sync(&adapter->devdump_work);
> >  	mwifiex_cancel_all_pending_cmd(adapter);
> >  	wake_up_interruptible(&adapter->cmd_wait_q.wait);
> >  	wake_up_interruptible(&adapter->hs_activate_wait_q);
> 
> In this patch please only do the API change in mwifiex. The change to
> using a workqueue needs to be in separate patch so it can be properly
> tested. I don't want a change like that going to the kernel without
> testing on a real device.

Thank you for your suggestions! I will only do the API change in mwifies and
keep other places that call dev_coredumpv remain unchanged. I will test the
new separate patches on real Marvell wifi chip these days.

Best regards,
Duoming Zhou