linux-kernel - Re: [PATCH] libperf: xyarray: Add bounds checks to xyarray_

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Date:   Thu, 15 Apr 2021 16:51:09 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] libperf: xyarray: Add bounds checks to xyarray__entry()

Em Thu, Apr 15, 2021 at 04:48:34PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Apr 15, 2021 at 04:46:46PM -0300, Arnaldo Carvalho de Melo escreveu:
> > 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@...nel.org> wrote:
> > > > > +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.
> 
> So...:
> 
>   CC       /tmp/build/perf/builtin-script.o
> In file included from xyarray.c:2:
> /home/acme/git/perf/tools/lib/perf/include/internal/xyarray.h: In function ‘xyarray__entry’:
> /home/acme/git/perf/tools/lib/perf/include/internal/xyarray.h:28:8: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
>    28 |  if (x >= xy->max_x || y >= xy->max_y)
>       |        ^~
> /home/acme/git/perf/tools/lib/perf/include/internal/xyarray.h:28:26: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
>    28 |  if (x >= xy->max_x || y >= xy->max_y)
>       |                          ^~
> cc1: all warnings being treated as errors
> 
> 
> Fedora 33's gcc complains, so I'll cast it to size_t.

> > > 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.

So I did this, should be enough:

diff --git a/tools/lib/perf/include/internal/xyarray.h b/tools/lib/perf/include/internal/xyarray.h
index f0896c00b4940016..f10af3da7b21cc15 100644
--- a/tools/lib/perf/include/internal/xyarray.h
+++ b/tools/lib/perf/include/internal/xyarray.h
@@ -23,7 +23,7 @@ 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)
+static inline void *xyarray__entry(struct xyarray *xy, size_t x, size_t y)
 {
 	if (x >= xy->max_x || y >= xy->max_y)
 		return NULL;