Re: [PATCH] libperf: xyarray: Add bounds checks to xyarray__entry()

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Apr 14, 2021 at 03:53:36PM -0500, Rob Herring escreveu:
> On Wed, Apr 14, 2021 at 3:25 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > On Thu, Apr 15, 2021 at 4:58 AM Rob Herring <robh@kernel.org> wrote:
> > >
> > > xyarray__entry() is missing any bounds checking yet often the x and y
> > > parameters come from external callers. Add bounds checks and an
> > > unchecked __xyarray__entry().
> > >
> > > Cc: Peter Zijlstra <peterz@infradead.org>
> > > Cc: Ingo Molnar <mingo@redhat.com>
> > > Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> > > Cc: Mark Rutland <mark.rutland@arm.com>
> > > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > > Cc: Jiri Olsa <jolsa@redhat.com>
> > > Cc: Namhyung Kim <namhyung@kernel.org>
> > > Signed-off-by: Rob Herring <robh@kernel.org>
> > > ---
> > >  tools/lib/perf/include/internal/xyarray.h | 9 ++++++++-
> > >  1 file changed, 8 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/tools/lib/perf/include/internal/xyarray.h b/tools/lib/perf/include/internal/xyarray.h
> > > index 51e35d6c8ec4..f0896c00b494 100644
> > > --- a/tools/lib/perf/include/internal/xyarray.h
> > > +++ b/tools/lib/perf/include/internal/xyarray.h
> > > @@ -18,11 +18,18 @@ struct xyarray *xyarray__new(int xlen, int ylen, size_t entry_size);
> > >  void xyarray__delete(struct xyarray *xy);
> > >  void xyarray__reset(struct xyarray *xy);
> > >
> > > -static inline void *xyarray__entry(struct xyarray *xy, int x, int y)
> > > +static inline void *__xyarray__entry(struct xyarray *xy, int x, int y)
> > >  {
> > >         return &xy->contents[x * xy->row_size + y * xy->entry_size];
> > >  }
> > >
> > > +static inline void *xyarray__entry(struct xyarray *xy, int x, int y)
> > > +{
> > > +       if (x >= xy->max_x || y >= xy->max_y)
> > > +               return NULL;
> >
> > Maybe better to check negatives as well.
> 
> max_x and max_y are size_t and unsigned, so x and y will be promoted
> to unsigned and the check will still work.

Fair enough, applied.

- Arnaldo
 
> It's probably better to change the args to size_t though. And perhaps
> on xyarray__new(), xyarray__max_y(), and xyarray__max_x() as well.