lib subcmd: Avoid segv/use-after-free when commands aren't excluded

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

Posted by Ian Rogers 2 years, 7 months ago

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@google.com>
---
 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

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

Posted by Namhyung Kim 2 years, 7 months ago

On Fri, Jul 7, 2023 at 4:09 PM Ian Rogers <irogers@google.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@google.com>

Acked-by: Namhyung Kim <namhyung@kernel.org>

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
>

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

Posted by Arnaldo Carvalho de Melo 2 years, 7 months ago

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@google.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@google.com>
> 
> Acked-by: Namhyung Kim <namhyung@kernel.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