linux-kernel - Re: [PATCH v2 11/25] usb: gadget: f_tcm: Execute command on write completion

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Yw0YP1qUYAw6inMJ@linutronix.de>
Date:   Mon, 29 Aug 2022 21:49:19 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dmitry Bogdanov <d.bogdanov@...ro.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>
Subject: Re: [PATCH v2 11/25] usb: gadget: f_tcm: Execute command on write
 completion

On 2022-08-26 18:37:36 [+0000], Thinh Nguyen wrote:
> On Fri, Aug 26, 2022, Sebastian Andrzej Siewior wrote:
> > On 2022-07-18 18:27:12 [-0700], Thinh Nguyen wrote:
> > > index 6fea80afe2d7..ec83f2f9a858 100644
> > > --- a/drivers/usb/gadget/function/f_tcm.c
> > > +++ b/drivers/usb/gadget/function/f_tcm.c
> > > @@ -955,7 +949,7 @@ static void usbg_data_write_cmpl(struct usb_ep *ep, struct usb_request *req)
> > >  				se_cmd->data_length);
> > >  	}
> > >  
> > > -	complete(&cmd->write_complete);
> > > +	target_execute_cmd(se_cmd);
> > 
> > usbg_data_write_cmpl() is invoked from interrupt service routing which
> > may run with disabled interrupts. From looking at target_execute_cmd():
> 
> It will always be called with interrupts disabled as documented in
> usb_request API.
> 
> > | void target_execute_cmd(struct se_cmd *cmd)
> > | {
> > …
> > |         spin_lock_irq(&cmd->t_state_lock);
> > …
> > |         spin_unlock_irq(&cmd->t_state_lock);
> > …
> > | }
> > 
> > which means interrupts will remain open after leaving
> > target_execute_cmd(). Now, why didn't the WARN_ONCE() in
> > __handle_irq_event_percpu() trigger? Am I missing something?
> > 
> > >  	return;
> > 
> 
> Since target_execute_cmd() is called in usbg_data_write_cmpl(),
> interrupts are still disabled.

but you do realize that target_execute_cmd() will leave with enabled
interrupts and this is not desired? I _think_ this was the reason why I
ended up with the wait+complete construct instead of invoking this
function directly.
An _irqsave() in target_execute_cmd() would probably be all you need
here.

> Thanks,
> Thinh

Sebastian