| Message ID | 20220715032233.230507-1-shaozhengchao@huawei.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [v3,bpf-next] bpf: Don't redirect packets with invalid pkt_len | expand |
On Fri, 15 Jul 2022 11:22:33 +0800 Zhengchao Shao wrote: > +#ifdef CONFIG_DEBUG_NET > + if (unlikely(!skb->len)) { > + pr_err("%s\n", __func__); > + skb_dump(KERN_ERR, skb, false); > + WARN_ON_ONCE(1); > + } Is there a reason to open code WARN_ONCE() like that? #ifdef CONFIG_DEBUG_NET if (WARN_ONCE(!skb->len, "%s\n", __func__)) skb_dump(KERN_ERR, skb, false); or if (IS_ENABLED(CONFIG_DEBUG_NET) && WARN_ONCE(!skb->len, "%s\n", __func__)) skb_dump(KERN_ERR, skb, false);
On Fri, Jul 15, 2022 at 6:30 AM Jakub Kicinski <kuba@kernel.org> wrote: > > On Fri, 15 Jul 2022 11:22:33 +0800 Zhengchao Shao wrote: > > +#ifdef CONFIG_DEBUG_NET > > + if (unlikely(!skb->len)) { > > + pr_err("%s\n", __func__); > > + skb_dump(KERN_ERR, skb, false); > > + WARN_ON_ONCE(1); > > + } > > Is there a reason to open code WARN_ONCE() like that? > > #ifdef CONFIG_DEBUG_NET > if (WARN_ONCE(!skb->len, "%s\n", __func__)) > skb_dump(KERN_ERR, skb, false); > > or > > if (IS_ENABLED(CONFIG_DEBUG_NET) && > WARN_ONCE(!skb->len, "%s\n", __func__)) > skb_dump(KERN_ERR, skb, false); Also the skb_dump() needs to be done once. DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false);
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f6a27ab19202..8ea41ad0786b 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2459,6 +2459,17 @@ static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset) #endif /* NET_SKBUFF_DATA_USES_OFFSET */ +static inline void skb_assert_len(struct sk_buff *skb) +{ +#ifdef CONFIG_DEBUG_NET + if (unlikely(!skb->len)) { + pr_err("%s\n", __func__); + skb_dump(KERN_ERR, skb, false); + WARN_ON_ONCE(1); + } +#endif /* CONFIG_DEBUG_NET */ +} + /* * Add data to an sk_buff */ diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 2ca96acbc50a..dc9dc0bedca0 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -955,6 +955,9 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb) { struct qdisc_skb_cb *cb = (struct qdisc_skb_cb *)skb->cb; + if (!skb->len) + return -EINVAL; + if (!__skb) return 0; diff --git a/net/core/dev.c b/net/core/dev.c index d588fd0a54ce..716df64fcfa5 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4168,6 +4168,7 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev) bool again = false; skb_reset_mac_header(skb); + skb_assert_len(skb); if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP)) __skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);
Syzbot found an issue [1]: fq_codel_drop() try to drop a flow whitout any skbs, that is, the flow->head is null. The root cause, as the [2] says, is because that bpf_prog_test_run_skb() run a bpf prog which redirects empty skbs. So we should determine whether the length of the packet modified by bpf prog or others like bpf_prog_test is valid before forwarding it directly. LINK: [1] https://syzkaller.appspot.com/bug?id=0b84da80c2917757915afa89f7738a9d16ec96c5 LINK: [2] https://www.spinics.net/lists/netdev/msg777503.html Reported-by: syzbot+7a12909485b94426aceb@syzkaller.appspotmail.com Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com> --- v2: need move checking to convert___skb_to_skb and add debug info v1: should not check len in fast path include/linux/skbuff.h | 11 +++++++++++ net/bpf/test_run.c | 3 +++ net/core/dev.c | 1 + 3 files changed, 15 insertions(+)