[libcamera-devel] [PATCH] libcamera: controls: guard ControlInfoMap against nullptr idmap_

[Laurent Pinchart]

On Wed, Apr 05, 2023 at 05:47:41AM +0300, Laurent Pinchart wrote:
> Hi Mattijs,
> 
> Thank you for the patch.
> 
> On Tue, Apr 04, 2023 at 06:11:16PM +0200, Mattijs Korpershoek via libcamera-devel wrote:
> > It's possible to construct a Camera with an unsafe controlInfo_.
> > This is the case in the Simple pipeline, where the camera controls are
> > not populated.
> > 
> > With Simple, if we attempt to set a Control, we end up with a segfault
> > because the default constructor for ControlInfoMap doesn't
> > intialized idmap_ which is initialized at class declaration time as
> > 
> >   const ControlIdMap *idmap_ = nullptr;
> > 
> > Add some safeguards in ControlInfoMap to handle this case.
> > 
> > Link: http://codepad.org/CiLLcPNW
> > Link: https://lists.libcamera.org/pipermail/libcamera-devel/2023-April/037439.html
> > Suggested-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
> > Signed-off-by: Mattijs Korpershoek <mkorpershoek at baylibre.com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Actually, maybe I ask you to extend the ControlInfoMap unit test to
catch the issue ? The test should crash without this patch, and pass
with it. This can be done in a separate patch.

> > ---
> > I have build-tested this against master and functionally tested on a
> > v0.0.4 android integration branch.
> > 
> > I've tested that i'm able to do a camera preview even when the
> > ScalerCrop control is unavailble.
> > 
> > Note that Jacopo already discussed alternative implementation by making
> > idmap_ an instance instead of a pointer, but that seemed not a good idea
> > either:
> > 
> > https://lists.libcamera.org/pipermail/libcamera-devel/2023-April/037439.html
> > ---
> >  src/libcamera/controls.cpp | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> > 
> > diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
> > index 6dbf9b348709..b808116c01e5 100644
> > --- a/src/libcamera/controls.cpp
> > +++ b/src/libcamera/controls.cpp
> > @@ -677,6 +677,9 @@ ControlInfoMap::ControlInfoMap(Map &&info, const ControlIdMap &idmap)
> >  
> >  bool ControlInfoMap::validate()
> >  {
> > +	if (!idmap_)
> > +		return false;
> > +
> >  	for (const auto &ctrl : *this) {
> >  		const ControlId *id = ctrl.first;
> >  		auto it = idmap_->find(id->id());
> > @@ -719,6 +722,8 @@ bool ControlInfoMap::validate()
> >   */
> >  ControlInfoMap::mapped_type &ControlInfoMap::at(unsigned int id)
> >  {
> > +	ASSERT(idmap_);
> > +
> >  	return at(idmap_->at(id));
> >  }
> >  
> > @@ -729,6 +734,8 @@ ControlInfoMap::mapped_type &ControlInfoMap::at(unsigned int id)
> >   */
> >  const ControlInfoMap::mapped_type &ControlInfoMap::at(unsigned int id) const
> >  {
> > +	ASSERT(idmap_);
> > +
> >  	return at(idmap_->at(id));
> >  }
> >  
> > @@ -739,6 +746,9 @@ const ControlInfoMap::mapped_type &ControlInfoMap::at(unsigned int id) const
> >   */
> >  ControlInfoMap::size_type ControlInfoMap::count(unsigned int id) const
> >  {
> > +	if (!idmap_)
> > +		return 0;
> > +
> >  	/*
> >  	 * The ControlInfoMap and its idmap have a 1:1 mapping between their
> >  	 * entries, we can thus just count the matching entries in idmap to
> > @@ -755,6 +765,9 @@ ControlInfoMap::size_type ControlInfoMap::count(unsigned int id) const
> >   */
> >  ControlInfoMap::iterator ControlInfoMap::find(unsigned int id)
> >  {
> > +	if (!idmap_)
> > +		return end();
> > +
> >  	auto iter = idmap_->find(id);
> >  	if (iter == idmap_->end())
> >  		return end();
> > @@ -770,6 +783,9 @@ ControlInfoMap::iterator ControlInfoMap::find(unsigned int id)
> >   */
> >  ControlInfoMap::const_iterator ControlInfoMap::find(unsigned int id) const
> >  {
> > +	if (!idmap_)
> > +		return end();
> > +
> >  	auto iter = idmap_->find(id);
> >  	if (iter == idmap_->end())
> >  		return end();
> > 
> > ---
> > base-commit: ac7511dc4c594f567ddff27ccc02c30bf6c00bfd
> > change-id: 20230404-guard-idmap-1d95f2100aca

-- 
Regards,

Laurent Pinchart