[PATCH v2 1/1] apps: cam: kms_sink: Verify colorSpace presence before dereference

[Laurent Pinchart]

On Tue, Dec 17, 2024 at 04:23:27PM +0000, Kieran Bingham wrote:
> Quoting Antoine Bouyer (2024-12-17 14:02:39)
> > During configuration stage, kms_sink doesn't check optional colorSpace
> > parameter is valid while dereferencing it. Then it leads to a crash
> > with below signature if parameter is not defined:
> > 
> >   /opt/fsl-imx-internal-xwayland/6.12-styhead/sysroots/armv8a-poky-linux/usr/include/c++/14.2.0/optional:48
> >   2: constexpr const _Tp& std::_Optional_base_impl<_Tp, _Dp>::_M_get() const [with _Tp = libcamera::ColorSp
> >   ace; _Dp = std::_Optional_base<libcamera::ColorSpace, true, true>]: Assertion 'this->_M_is_engaged()' fai
> >   led.
> >   Aborted (core dumped)
> > 
> > This behavior is confirmed in the "operator->" page:
> >  (https://en.cppreference.com/w/cpp/utility/optional/operator*)
> > 
> > "This operator does not check whether the optional contains a value!"
> > 
> > This crash is observed with styhead's gcc compiler (version 14.2.0),
> > while it was not with previous scarthgap's gcc compiler (version 13.2.0).
> > 
> > Use has_value() as a fix to make sure this property exists and prevent
> > crash.
> > 
> > Fixes: 6d7ddace5278 ("cam: Add KMS sink class")
> > Signed-off-by: Antoine Bouyer <antoine.bouyer at nxp.com>
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> Thanks for the updates that I suggested, however I'm weary that perhaps
> Laurent was suggesting this /shouldn't/ be possible to happen and should
> be fixed in the pipeline handler? (and perhaps enforced?, and maybe
> guaranteed to be set to RAW if unknown?)
> 
> We could perhaps have a common path in the configuration that sets RAW
> when the pipeline handler didn't set it ? Or maybe we enforce it must be
> set by lc-compliance or such...

Let's see first, Antoine, which pipeline handler have you encountered
this issue with ?

> > ---
> >  src/apps/cam/kms_sink.cpp | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/apps/cam/kms_sink.cpp b/src/apps/cam/kms_sink.cpp
> > index 672c985..8f3b867 100644
> > --- a/src/apps/cam/kms_sink.cpp
> > +++ b/src/apps/cam/kms_sink.cpp
> > @@ -153,7 +153,8 @@ int KMSSink::configure(const libcamera::CameraConfiguration &config)
> >         colorEncoding_ = std::nullopt;
> >         colorRange_ = std::nullopt;
> >  
> > -       if (cfg.colorSpace->ycbcrEncoding == libcamera::ColorSpace::YcbcrEncoding::None)
> > +       if (!cfg.colorSpace.has_value() ||
> > +           cfg.colorSpace->ycbcrEncoding == libcamera::ColorSpace::YcbcrEncoding::None)
> >                 return 0;
> >  
> >         /*

-- 
Regards,

Laurent Pinchart