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From: Di Zhu <zhudi2@huawei.com>
To: <ast@kernel.org>, <edumazet@google.com>, <daniel@iogearbox.net>,
	<andrii@kernel.org>, <yhs@fb.com>, <davem@davemloft.net>
Cc: <netdev@vger.kernel.org>, <bpf@vger.kernel.org>,
	<zhudi2@huawei.com>, <rose.chen@huawei.com>,
	<syzbot+7a12909485b94426aceb@syzkaller.appspotmail.com>
Subject: [PATCH] bpf: Don't redirect packets with pkt_len 0
Date: Fri, 17 Jun 2022 15:18:55 +0800	[thread overview]
Message-ID: <20220617071855.2482-1-zhudi2@huawei.com> (raw)

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 0 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: Di Zhu <zhudi2@huawei.com>
---
 net/core/filter.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 5af58eb48587..c7fbfa90898a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2156,6 +2156,9 @@ static int __bpf_redirect_common(struct sk_buff *skb, struct net_device *dev,
 static int __bpf_redirect(struct sk_buff *skb, struct net_device *dev,
 			  u32 flags)
 {
+	if (unlikely(skb->len == 0))
+		return -EINVAL;
+
 	if (dev_is_mac_header_xmit(dev))
 		return __bpf_redirect_common(skb, dev, flags);
 	else
-- 
2.27.0


             reply	other threads:[~2022-06-17  7:19 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-17  7:18 Di Zhu [this message]
2022-06-17  8:10 ` [PATCH] bpf: Don't redirect packets with pkt_len 0 Eric Dumazet
2022-06-18 10:16 zhudi (E)

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