linux-kernel - Re: [PATCH v2] lib subcmd: Avoid segv/use-after-free when commands aren't excluded

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Message-ID: <ZK2xk2qJE2M+bGCb@kernel.org>
Date:   Tue, 11 Jul 2023 16:46:27 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Chenyuan Mi <cymi20@...an.edu.cn>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] lib subcmd: Avoid segv/use-after-free when commands
 aren't excluded

Em Tue, Jul 11, 2023 at 10:36:59AM -0700, Namhyung Kim escreveu:
> On Fri, Jul 7, 2023 at 4:09 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > The array shortening may perform unnecessary array copies. Before
> > commit 657a3efee43a ("lib subcmd: Avoid memory leak in exclude_cmds")
> > this was benign, but afterwards this could lead to a segv.
> >
> > Fixes: 657a3efee43a ("lib subcmd: Avoid memory leak in exclude_cmds")
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> 
> Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks, applied to perf-tools.

- Arnaldo

 
> Thanks,
> Namhyung
> 
> 
> > ---
> >  tools/lib/subcmd/help.c | 18 ++++++++++++------
> >  1 file changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/lib/subcmd/help.c b/tools/lib/subcmd/help.c
> > index 67a8d6b740ea..adfbae27dc36 100644
> > --- a/tools/lib/subcmd/help.c
> > +++ b/tools/lib/subcmd/help.c
> > @@ -68,8 +68,13 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
> >         while (ci < cmds->cnt && ei < excludes->cnt) {
> >                 cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name);
> >                 if (cmp < 0) {
> > -                       zfree(&cmds->names[cj]);
> > -                       cmds->names[cj++] = cmds->names[ci++];
> > +                       if (ci == cj) {
> > +                               ci++;
> > +                               cj++;
> > +                       } else {
> > +                               zfree(&cmds->names[cj]);
> > +                               cmds->names[cj++] = cmds->names[ci++];
> > +                       }
> >                 } else if (cmp == 0) {
> >                         ci++;
> >                         ei++;
> > @@ -77,10 +82,11 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
> >                         ei++;
> >                 }
> >         }
> > -
> > -       while (ci < cmds->cnt) {
> > -               zfree(&cmds->names[cj]);
> > -               cmds->names[cj++] = cmds->names[ci++];
> > +       if (ci != cj) {
> > +               while (ci < cmds->cnt) {
> > +                       zfree(&cmds->names[cj]);
> > +                       cmds->names[cj++] = cmds->names[ci++];
> > +               }
> >         }
> >         for (ci = cj; ci < cmds->cnt; ci++)
> >                 zfree(&cmds->names[ci]);
> > --
> > 2.41.0.390.g38632f3daf-goog
> >

-- 

- Arnaldo