Re: [PATCH net] net/sched: cls_api: Initialize miss_cookie_node when action miss is not used

[Ivan Vecera]

On 20. 04. 23 20:21, Pedro Tammela wrote:
> On 20/04/2023 14:59, Ivan Vecera wrote:
> > Function tcf_exts_init_ex() sets exts->miss_cookie_node ptr only
> > when use_action_miss is true so it assumes in other case that
> > the field is set to NULL by the caller. If not then the field
> > contains garbage and subsequent tcf_exts_destroy() call results
> > in a crash.
> > Initialize .miss_cookie_node pointer to NULL when use_action_miss
> > parameter is false to avoid this potential scenario.
> >
> > Fixes: 80cd22c35c90 ("net/sched: cls_api: Support hardware miss to tc 
> > action")
> > Signed-off-by: Ivan Vecera <ivecera@xxxxxxxxxx>
> > ---
> >   net/sched/cls_api.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> > index 35785a36c80298..8bc5b9d6a2916e 100644
> > --- a/net/sched/cls_api.c
> > +++ b/net/sched/cls_api.c
> > @@ -3224,8 +3224,12 @@ int tcf_exts_init_ex(struct tcf_exts *exts, 
> > struct net *net, int action,
> >       exts->action = action;
> >       exts->police = police;
> > -    if (!use_action_miss)
> > +    if (!use_action_miss) {
> > +#ifdef CONFIG_NET_CLS_ACT
> > +        exts->miss_cookie_node = NULL;
> > +#endif
> >           return 0;
> > +    }
> >       err = tcf_exts_miss_cookie_base_alloc(exts, tp, handle);
> >       if (err)
>
> The problem described here also happens in the case some error happens 
> if the action array allocation fails and before the 'miss_cookie_node' 
> assignment inside 'tcf_exts_miss_cookie_base_alloc()'.
>
> Seems like a better way to solve this issue is to just:
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 35785a36c802..3c3629c9e7b6 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -3211,6 +3211,7 @@ int tcf_exts_init_ex(struct tcf_exts *exts, struct 
> net *net, int action,
>   #ifdef CONFIG_NET_CLS_ACT
>          exts->type = 0;
>          exts->nr_actions = 0;
> +       exts->miss_cookie_node = NULL;
>          /* Note: we do not own yet a reference on net.
>           * This reference might be taken later from tcf_exts_get_net().
>           */

Looks better, will repost...

Thanks

Ivan