From: Martin KaFai Lau <martin.lau@linux.dev>
To: Zhengchao Shao <shaozhengchao@huawei.com>
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
song@kernel.org, yhs@fb.com, john.fastabend@gmail.com,
kpsingh@kernel.org, sdf@google.com, bigeasy@linutronix.de,
imagedong@tencent.com, petrm@nvidia.com, arnd@arndb.de,
dsahern@kernel.org, talalahmad@google.com, keescook@chromium.org,
haoluo@google.com, jolsa@kernel.org, weiyongjun1@huawei.com,
yuehaibing@huawei.com, bpf@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, hawk@kernel.org
Subject: Re: [PATCH v4,bpf-next] bpf: Don't redirect packets with invalid pkt_len
Date: Thu, 3 Nov 2022 14:07:44 -0700 [thread overview]
Message-ID: <f0bb3cd6-6986-6ca1-aa40-7a10302c8586@linux.dev> (raw)
In-Reply-To: <20220715115559.139691-1-shaozhengchao@huawei.com>
On 7/15/22 4:55 AM, Zhengchao Shao wrote:
> 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>
> ---
> v3: modify debug print
> 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 | 8 ++++++++
> net/bpf/test_run.c | 3 +++
> net/core/dev.c | 1 +
> 3 files changed, 12 insertions(+)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index f6a27ab19202..82e8368ba6e6 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2459,6 +2459,14 @@ 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 (WARN_ONCE(!skb->len, "%s\n", __func__))
> + DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false);
> +#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;
From another recent report [0], I don't think this change is fixing the report
from syzbot. It probably makes sense to revert this patch.
afaict, This '!skb->len' test is done after
if (is_l2)
__skb_push(skb, hh_len);
Hence, skb->len is not zero in convert___skb_to_skb(). The proper place to test
skb->len is before __skb_push() to ensure there is some network header after the
mac or may as well ensure "data_size_in > ETH_HLEN" at the beginning.
The fix in [0] is applied. If it turns out there are other cases caused by the
skb generated by test_run that needs extra fixes in bpf_redirect_*, it needs to
revisit an earlier !skb->len check mentioned above and the existing test cases
outside of test_progs would have to adjust accordingly.
[0]: https://lore.kernel.org/bpf/20221027225537.353077-1-sdf@google.com/
> +
> 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);
next prev parent reply other threads:[~2022-11-03 21:10 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-15 11:55 [PATCH v4,bpf-next] bpf: Don't redirect packets with invalid pkt_len Zhengchao Shao
2022-07-15 23:30 ` Stanislav Fomichev
2022-07-19 17:00 ` patchwork-bot+netdevbpf
2022-09-14 11:19 ` Lorenz Bauer
2022-09-17 15:46 ` Stanislav Fomichev
2022-09-19 10:55 ` shaozhengchao
2022-09-20 14:42 ` Lorenz Bauer
2022-09-21 8:48 ` shaozhengchao
2022-09-21 20:59 ` Stanislav Fomichev
2022-10-13 9:36 ` Lorenz Bauer
2022-10-13 10:44 ` shaozhengchao
2022-10-14 16:29 ` Lorenz Bauer
2022-10-14 16:55 ` sdf
2022-10-15 2:36 ` shaozhengchao
2022-11-03 21:07 ` Martin KaFai Lau [this message]
2022-11-03 21:36 ` Stanislav Fomichev
2022-11-03 22:42 ` Martin KaFai Lau
2022-11-03 22:58 ` Stanislav Fomichev
2022-11-09 21:43 ` Stanislav Fomichev
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f0bb3cd6-6986-6ca1-aa40-7a10302c8586@linux.dev \
--to=martin.lau@linux.dev \
--cc=andrii@kernel.org \
--cc=arnd@arndb.de \
--cc=ast@kernel.org \
--cc=bigeasy@linutronix.de \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=dsahern@kernel.org \
--cc=edumazet@google.com \
--cc=haoluo@google.com \
--cc=hawk@kernel.org \
--cc=imagedong@tencent.com \
--cc=john.fastabend@gmail.com \
--cc=jolsa@kernel.org \
--cc=keescook@chromium.org \
--cc=kpsingh@kernel.org \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=petrm@nvidia.com \
--cc=sdf@google.com \
--cc=shaozhengchao@huawei.com \
--cc=song@kernel.org \
--cc=talalahmad@google.com \
--cc=weiyongjun1@huawei.com \
--cc=yhs@fb.com \
--cc=yuehaibing@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).