Re: [ovs-dev] [PATCH net-next v5 02/10] net: sched: act_sample: add action cookie to sample
On 26 Jun 2024, at 22:06, Adrián Moreno wrote:
> 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
>>> ---
>>> 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.
ACK, confirmed that [1] seems to be the only way to set the cookie. So this
patch seems fine to me too.
Acked-by: Eelco Chaudron
> 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
>>
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Re: [ovs-dev] [PATCH net-next v5 02/10] net: sched: act_sample: add action cookie to sample
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
> > ---
> > 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
>
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Re: [ovs-dev] [PATCH net-next v5 02/10] net: sched: act_sample: add action cookie to sample
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
> ---
> 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))
> + 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
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Re: [ovs-dev] [PATCH net-next v5 02/10] net: sched: act_sample: add action cookie to sample
On Tue, Jun 25, 2024 at 10:51:45PM +0200, 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 Reviewed-by: Ido Schimmel ___ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
[ovs-dev] [PATCH net-next v5 02/10] net: sched: act_sample: add action cookie to sample
If the action has a user_cookie, pass it along to the sample so it can
be easily identified.
Signed-off-by: Adrian Moreno
---
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);
+ 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
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