[PATCH 2/3] libcamera: shared_mem_object: Prevent memfd from shrinking or growing

[Laurent Pinchart]

On Wed, Jul 31, 2024 at 09:40:11AM +0100, Kieran Bingham wrote:
> Quoting Milan Zamazal (2024-07-31 08:24:29)
> > Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:
> > 
> > > The memfd underlying the SharedMem object must not shrink, or memory
> > > corruption will happen. Prevent this by setting the shrink seal on the
> > > file. As there's no valid use case for growing the memory either, set
> > > the grow seal as well.
> > 
> > Makes sense to me.
> > 
> > Reviewed-by: Milan Zamazal <mzamazal at redhat.com>
> 
> Haha, I was going to ask about this in the previous patch - then I
> discovered this ;-)
> 
> But should we - with the same logic also add MemFd::Seal::Grow to the
> allocFromUDmaBuf() implementation too?

I think we could. Do you want to submit a patch ? :-)

> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > > ---
> > >  src/libcamera/shared_mem_object.cpp | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/src/libcamera/shared_mem_object.cpp b/src/libcamera/shared_mem_object.cpp
> > > index 022645e71a35..d4c7991ad16a 100644
> > > --- a/src/libcamera/shared_mem_object.cpp
> > > +++ b/src/libcamera/shared_mem_object.cpp
> > > @@ -58,7 +58,8 @@ SharedMem::SharedMem() = default;
> > >   */
> > >  SharedMem::SharedMem(const std::string &name, std::size_t size)
> > >  {
> > > -     UniqueFD memfd = MemFd::create(name.c_str(), size);
> > > +     UniqueFD memfd = MemFd::create(name.c_str(), size, MemFd::Seal::Shrink |
> > > +                                    MemFd::Seal::Grow);
> > >       if (!memfd.isValid())
> > >               return;

-- 
Regards,

Laurent Pinchart