Re: [PATCH] goku_udc: Add check for NULL in goku_irq

[Анастасия Белова]

03.02.2023 13:45, Greg Kroah-Hartman пишет:
> On Fri, Feb 03, 2023 at 01:18:28PM +0300, Anastasia Belova wrote:
> > Before dereferencing dev->driver check it for NULL.
> >
> > If an interrupt handler is called after assigning
> > NULL to dev->driver, but before resetting dev->int_enable,
> > NULL-pointer will be dereferenced.
> >
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > Signed-off-by: Anastasia Belova <abelova@xxxxxxxxxxxxx>
> > ---
> >   drivers/usb/gadget/udc/goku_udc.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/udc/goku_udc.c b/drivers/usb/gadget/udc/goku_udc.c
> > index bdc56b24b5c9..896bba8b47f1 100644
> > --- a/drivers/usb/gadget/udc/goku_udc.c
> > +++ b/drivers/usb/gadget/udc/goku_udc.c
> > @@ -1616,8 +1616,9 @@ static irqreturn_t goku_irq(int irq, void *_dev)
> >   pm_next:
> >   		if (stat & INT_USBRESET) {		/* hub reset done */
> >   			ACK(INT_USBRESET);
> > -			INFO(dev, "USB reset done, gadget %s\n",
> > -				dev->driver->driver.name);
> > +			if (dev->driver)
> > +				INFO(dev, "USB reset done, gadget %s\n",
> > +					dev->driver->driver.name);
> How can this ever happen?  Can you trigger this somehow?  If not, I
> don't think this is going to be possible (also what's up with printk
> from an irq handler???)

Unfortunately, I can't find the way to trigger this at the moment.

What about printk, should trace_printk be used instead?

> Odds are, no one actually has this hardware anymore, right?

Despite of this, such vulnerability should be fixed because

there is a possibility to exploit it.

> thanks,
>
> greg k-h

Best regards,

Anastasia Belova