5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ 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: 1def9238d4aa ("net_sched: more precise pkt_len computation")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/core/dev.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 5e75359acd0c5..8f2f14df3610b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3383,10 +3383,14 @@ 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;
}
}
--
2.43.0
