Re: [PATCH RFC 1/3] i2c: bcm2835: Avoid possible NULL ptr dereference

[Stefan Wahren <stefan.wahren-eS4NqCHxEME@public.gmane.org>]

Hi,

> Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org> hat am 18. Februar 2017 um 19:34 geschrieben:
> 
> 
> 
> Den 16.02.2017 22.20, skrev Stefan Wahren:
> > Since commit e2474541032d ("bcm2835: Fix hang for writing messages
> > larger than 16 bytes") the interrupt handler is prone to a possible
> > NULL pointer dereference. This could happen if an interrupt fires
> > before curr_msg is set by bcm2835_i2c_xfer_msg() and randomly occurs
> > on the RPi 3. Even this is an unexpected behavior the driver must
> > handle that with an error instead of a crash.
> >
> > CC: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
> > CC: Martin Sperl <kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org>
> > Reported-by: Peter Robinson <pbrobinson-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > Fixes: e2474541032d ("bcm2835: Fix hang for writing messages larger than 16 bytes")
> > Signed-off-by: Stefan Wahren <stefan.wahren-eS4NqCHxEME@public.gmane.org>
> > ---
> >   drivers/i2c/busses/i2c-bcm2835.c |    4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
> > index c3436f6..10e39c8 100644
> > --- a/drivers/i2c/busses/i2c-bcm2835.c
> > +++ b/drivers/i2c/busses/i2c-bcm2835.c
> > @@ -195,7 +195,9 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
> >   	}
> >   
> >   	if (val & BCM2835_I2C_S_DONE) {
> > -		if (i2c_dev->curr_msg->flags & I2C_M_RD) {
> > +		if (!i2c_dev->curr_msg) {
> > +			dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
> > +		} else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
> >   			bcm2835_drain_rxfifo(i2c_dev);
> >   			val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
> >   		}
> 
> Thanks,
> 
> Acked-by: Noralf Trønnes <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
>

thanks, but i would be more happier to receive feedback for patches 2 and 3.

Stefan
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