On Wed, Jun 26, 2024 at 04:28:01PM GMT, Eelco Chaudron wrote: > > > On 25 Jun 2024, at 22:51, Adrian Moreno wrote: > > > If the action has a user_cookie, pass it along to the sample so it can > > be easily identified. > > > > Signed-off-by: Adrian Moreno <amore...@redhat.com> > > --- > > net/sched/act_sample.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/net/sched/act_sample.c b/net/sched/act_sample.c > > index a69b53d54039..2ceb4d141b71 100644 > > --- a/net/sched/act_sample.c > > +++ b/net/sched/act_sample.c > > @@ -167,7 +167,9 @@ TC_INDIRECT_SCOPE int tcf_sample_act(struct sk_buff > > *skb, > > { > > struct tcf_sample *s = to_sample(a); > > struct psample_group *psample_group; > > + u8 cookie_data[TC_COOKIE_MAX_SIZE]; > > struct psample_metadata md = {}; > > + struct tc_cookie *user_cookie; > > int retval; > > > > tcf_lastuse_update(&s->tcf_tm); > > @@ -189,6 +191,16 @@ TC_INDIRECT_SCOPE int tcf_sample_act(struct sk_buff > > *skb, > > if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev)) > > skb_push(skb, skb->mac_len); > > > > + rcu_read_lock(); > > + user_cookie = rcu_dereference(a->user_cookie); > > + if (user_cookie) { > > + memcpy(cookie_data, user_cookie->data, > > + user_cookie->len); > > Maybe I’m over paranoid, but can we assume user_cookie->len, will not be > larger than TC_COOKIE_MAX_SIZE? > Or should we do something like min(user_cookie->len, sizeof(cookie_data)) >
I think it's good to be paranoid with this kind of things. I do, however, think it should be safe to use. The cookie is extracted from the netlink attribute directly and its length is verified with the nla_policy [1]. So nothing that comes into the kernel should be larger than TC_COOKIE_MAX_SIZE. I guess if there is some previous bug that allows for the size to get corrupted, then this might happen but doing those kind of checks in the fast path seems a bit excessive. For example, Ilya argued in v2 [2] that we should avoid zeroing "u8 cookie_data[TC_COOKIE_MAX_SIZE]" to safe the unneeded cycles. [1] https://github.com/torvalds/linux/blob/55027e689933ba2e64f3d245fb1ff185b3e7fc81/net/sched/act_api.c#L1299 [2] https://patchwork.kernel.org/project/netdevbpf/patch/20240603185647.2310748-3-amore...@redhat.com/ Thanks. Adrián > > + md.user_cookie = cookie_data; > > + md.user_cookie_len = user_cookie->len; > > + } > > + rcu_read_unlock(); > > + > > md.trunc_size = s->truncate ? s->trunc_size : skb->len; > > psample_sample_packet(psample_group, skb, s->rate, &md); > > > > -- > > 2.45.1 > _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev