4.19-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ 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@google.com Reviewed-by: Willem de Bruijn willemb@google.com Reviewed-by: David Ahern dsahern@kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 916a095eaee27..0409c051ed5d4 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3443,10 +3443,14 @@ 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; } }