netdev - Re: [PATCH net] net/sched: act_ct: fix miss set mru for ovs after defrag in act

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAM_iQpXHu=6+c0HkutK5Bb5DoxM8fbas1Z6r6EC+tEXMGdudGw@mail.gmail.com>
Date:   Thu, 30 Jul 2020 14:50:19 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     wenxu <wenxu@...oud.cn>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net/sched: act_ct: fix miss set mru for ovs after
 defrag in act_ct

On Thu, Jul 30, 2020 at 1:53 AM wenxu <wenxu@...oud.cn> wrote:
>
>
> On 7/30/2020 2:03 PM, Cong Wang wrote:
> > On Wed, Jul 29, 2020 at 3:41 AM <wenxu@...oud.cn> wrote:
> >> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> >> index c510b03..45401d5 100644
> >> --- a/include/net/sch_generic.h
> >> +++ b/include/net/sch_generic.h
> >> @@ -384,6 +384,7 @@ struct qdisc_skb_cb {
> >>         };
> >>  #define QDISC_CB_PRIV_LEN 20
> >>         unsigned char           data[QDISC_CB_PRIV_LEN];
> >> +       u16                     mru;
> >>  };
> > Hmm, can you put it in the anonymous struct before 'data'?
> >
> > We validate this cb size and data size like blow:
> >
> > static inline void qdisc_cb_private_validate(const struct sk_buff *skb, int sz)
> > {
> >         struct qdisc_skb_cb *qcb;
> >
> >         BUILD_BUG_ON(sizeof(skb->cb) < offsetof(struct qdisc_skb_cb,
> > data) + sz);
> >         BUILD_BUG_ON(sizeof(qcb->data) < sz);
> > }
> >
> > It _kinda_ expects ->data at the end.
>
> It seems the data offsetof data should be align with szieof(u64)?
>
> If I  modify it as following
>
> @@ -383,6 +383,9 @@ struct qdisc_skb_cb {
>                 unsigned int            pkt_len;
>                 u16                     slave_dev_queue_mapping;
>                 u16                     tc_classid;
> +               u16                     mru;
>         };
>  #define QDISC_CB_PRIV_LEN 20
>         unsigned char           data[QDISC_CB_PRIV_LEN];
>
> compile fail:
>
> net/core/filter.c:7625:3: note: in expansion of macro ‘BUILD_BUG_ON’
>    BUILD_BUG_ON((offsetof(struct sk_buff, cb) +
>
> inn the file:  net/core/filter.c
>
> case offsetof(struct __sk_buff, cb[0]) ...
>
>              offsetofend(struct __sk_buff, cb[4]) - 1:
>                 BUILD_BUG_ON(sizeof_field(struct qdisc_skb_cb, data) < 20);
>                 BUILD_BUG_ON((offsetof(struct sk_buff, cb) +
>                               offsetof(struct qdisc_skb_cb, data)) %
>                              sizeof(__u64));
>
>
> If I  modify it as following
>
> @@ -383,6 +383,9 @@ struct qdisc_skb_cb {
>                 unsigned int            pkt_len;
>                 u16                     slave_dev_queue_mapping;
>                 u16                     tc_classid;
> +               u16                     mru;
> +               u16                     _pad1;
> +               u32                     _pad2;
>         };
>  #define QDISC_CB_PRIV_LEN 20
>         unsigned char           data[QDISC_CB_PRIV_LEN];
>
>
> compile fail:
>
> ./include/linux/filter.h:633:2: note: in expansion of macro ‘BUILD_BUG_ON’
>   BUILD_BUG_ON(sizeof(*cb) > sizeof_field(struct sk_buff, cb));
>
>
> static inline void bpf_compute_data_pointers(struct sk_buff *skb)
> {
>         struct bpf_skb_data_end *cb = (struct bpf_skb_data_end *)skb->cb;
>
>         BUILD_BUG_ON(sizeof(*cb) > sizeof_field(struct sk_buff, cb));
>         cb->data_meta = skb->data - skb_metadata_len(skb);
>         cb->data_end  = skb->data + skb_headlen(skb);
> }
>
>
> It seems no space for new value add before 'data'?

Hmm, I didn't know bpf has such restrictions on qdisc_skb_cb.
It seems impossible to add a new field before data, if you keep it
after data, can you adjust qdisc_cb_private_validate() too, like below?

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index c510b03b9751..68235489a5d4 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -463,7 +463,7 @@ static inline void qdisc_cb_private_validate(const
struct sk_buff *skb, int sz)
 {
        struct qdisc_skb_cb *qcb;

-       BUILD_BUG_ON(sizeof(skb->cb) < offsetof(struct qdisc_skb_cb,
data) + sz);
+       BUILD_BUG_ON(sizeof(skb->cb) < sizeof(*qcb));
        BUILD_BUG_ON(sizeof(qcb->data) < sz);
 }

Thanks.