2023-07-07 23:14:25

by Ian Rogers

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

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 <[email protected]>
---
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

2023-07-11 18:00:26

by Namhyung Kim

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

On Fri, Jul 7, 2023 at 4:09 PM Ian Rogers <[email protected]> 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 <[email protected]>

Acked-by: Namhyung Kim <[email protected]>

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
>

2023-07-11 20:04:59

by Arnaldo Carvalho de Melo

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 <[email protected]> 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 <[email protected]>
>
> Acked-by: Namhyung Kim <[email protected]>

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