On Tue, Jan 12, 2021 at 3:52 AM Xin Long <lucien....@gmail.com> wrote:
>
> On Tue, Jan 12, 2021 at 10:56 AM Cong Wang <xiyou.wangc...@gmail.com> wrote:
> >
> > From: Cong Wang <cong.w...@bytedance.com>
> >
> > fl_set_enc_opt() simply checks if there are still bytes left to parse,
> > but this is not sufficent as syzbot seems to be able to generate
> > malformatted netlink messages. nla_ok() is more strict so should be
> > used to validate the next nlattr here.
> >
> > And nla_validate_nested_deprecated() has less strict check too, it is
> > probably too late to switch to the strict version, but we can just
> > call nla_ok() too after it.
> >
> > Reported-and-tested-by:
> > syzbot+2624e3778b18fc497...@syzkaller.appspotmail.com
> > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> > Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> > Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuu...@netronome.com>
> > Cc: Jamal Hadi Salim <j...@mojatatu.com>
> > Cc: Xin Long <lucien....@gmail.com>
> > Cc: Jiri Pirko <j...@resnulli.us>
> > Signed-off-by: Cong Wang <cong.w...@bytedance.com>
> > ---
> > net/sched/cls_flower.c | 8 +++++---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> > index 1319986693fc..e265c443536e 100644
> > --- a/net/sched/cls_flower.c
> > +++ b/net/sched/cls_flower.c
> > @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct
> > fl_flow_key *key,
> >
> > nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > + if (!nla_ok(nla_opt_msk, msk_depth))
> > + return -EINVAL;
> > }
> I think it's better to also add NL_SET_ERR_MSG(extack, xxxx);
> for this error return, like all the other places in this function.
I think ext message is primarily for end users who usually can not
generate malformat netlink messages.
On the other hand, the nla_validate_nested_deprecated() right above
the quoted code does not set ext message either.
Thanks.
