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

[Kieran Bingham]

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...



> ---
>  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;
>  
>         /*
> -- 
> 2.34.1
>