Commit 668d838e authored by Eric Dumazet's avatar Eric Dumazet Committed by Liu Jian
Browse files

net: add more sanity checks to qdisc_pkt_len_init() 

stable inclusion
from stable-v6.6.55
commit 9b0ee571d20a238a22722126abdfde61f1b2bdd0
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYR8W
CVE: CVE-2024-49948

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9b0ee571d20a238a22722126abdfde61f1b2bdd0



-------------------------------------------------

[ Upstream commit ab9a9a9e9647392a19e7a885b08000e89c86b535 ]

One path takes care of SKB_GSO_DODGY, assuming
skb->len is bigger than hdr_len.

virtio_net_hdr_to_skb() does not fully dissect TCP headers,
it only make sure it is at least 20 bytes.

It is possible for an user to provide a malicious 'GSO' packet,
total length of 80 bytes.

- 20 bytes of IPv4 header
- 60 bytes TCP header
- a small gso_size like 8

virtio_net_hdr_to_skb() would declare this packet as a normal
GSO packet, because it would see 40 bytes of payload,
bigger than gso_size.

We need to make detect this case to not underflow
qdisc_skb_cb(skb)->pkt_len.

Fixes: 1def9238 ("net_sched: more precise pkt_len computation")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarLiu Jian <liujian56@huawei.com>
parent be251396

net/core/dev.c

+7 −3
Original line number Diff line number Diff line
@@ -3754,10 +3754,14 @@ static void qdisc_pkt_len_init(struct sk_buff *skb) 
				hdr_len += sizeof(struct udphdr);

		}



		if (shinfo->gso_type & SKB_GSO_DODGY)

			gso_segs = DIV_ROUND_UP(skb->len - hdr_len,

						shinfo->gso_size);

		if (unlikely(shinfo->gso_type & SKB_GSO_DODGY)) {

			int payload = skb->len - hdr_len;



			/* Malicious packet. */

			if (payload <= 0)

				return;

			gso_segs = DIV_ROUND_UP(payload, shinfo->gso_size);

		}

		qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len;

	}

}