Re: [PATCH] media: stm32: dcmipp: correct error handling in dcmipp_create_subdevs

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Hans,

On Thu, Jun 27, 2024 at 01:17:55PM +0200, Hans Verkuil wrote:
> On 24/06/2024 10:41, Alain Volmat wrote:
> > Correct error handling within the dcmipp_create_subdevs by properly
> > decrementing the i counter when releasing the subdeves.
> > 
> > Fixes: 28e0f3772296 ("media: stm32-dcmipp: STM32 DCMIPP camera interface driver")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
> > ---
> >  drivers/media/platform/st/stm32/stm32-dcmipp/dcmipp-core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/platform/st/stm32/stm32-dcmipp/dcmipp-core.c b/drivers/media/platform/st/stm32/stm32-dcmipp/dcmipp-core.c
> > index 4acc3b90d03a..4924ee36cfda 100644
> > --- a/drivers/media/platform/st/stm32/stm32-dcmipp/dcmipp-core.c
> > +++ b/drivers/media/platform/st/stm32/stm32-dcmipp/dcmipp-core.c
> > @@ -202,7 +202,7 @@ static int dcmipp_create_subdevs(struct dcmipp_device *dcmipp)
> >  	return 0;
> >  
> >  err_init_entity:
> > -	while (i > 0)
> > +	while (i-- > 0)
> >  		dcmipp->pipe_cfg->ents[i - 1].release(dcmipp->entity[i - 1]);
> >  	return ret;
> >  }
> 
> I accidentally merged this one, but this patch isn't right.
> 
> After this change the [i - 1] indices should be changed to [i].
> If i == 1, then the while condition is true, but now i == 0 in the
> actual statement, so you access out-of-bounds values.

Right. I think the best way to fix this would be to just remove "- 1"
inside the array indices. One could think this as a different bug but of
course with an unpleasant side effect which you get after fixing the first
bug.

> 
> I decided to revert it, since it is better to just get stuck in the
> while loop, then to crash.
> 
> But a new patch is needed for this.

-- 
Regards,

Sakari Ailus