The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6dd912f82680761d8fb6b1bb274a69d4c7010988 Mon Sep 17 00:00:00 2001
From: Willem de Bruijn willemb@google.com Date: Mon, 25 May 2020 15:07:40 -0400 Subject: [PATCH] net: check untrusted gso_size at kernel entry
Syzkaller again found a path to a kernel crash through bad gso input: a packet with gso size exceeding len.
These packets are dropped in tcp_gso_segment and udp[46]_ufo_fragment. But they may affect gso size calculations earlier in the path.
Now that we have thlen as of commit 9274124f023b ("net: stricter validation of untrusted gso packets"), check gso_size at entry too.
Fixes: bfd5f4a3d605 ("packet: Add GSO/csum offload support.") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index 6f6ade63b04c..88997022a4b5 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -31,6 +31,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, { unsigned int gso_type = 0; unsigned int thlen = 0; + unsigned int p_off = 0; unsigned int ip_proto;
if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) { @@ -68,7 +69,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, if (!skb_partial_csum_set(skb, start, off)) return -EINVAL;
- if (skb_transport_offset(skb) + thlen > skb_headlen(skb)) + p_off = skb_transport_offset(skb) + thlen; + if (p_off > skb_headlen(skb)) return -EINVAL; } else { /* gso packets without NEEDS_CSUM do not set transport_offset. @@ -92,17 +94,25 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, return -EINVAL; }
- if (keys.control.thoff + thlen > skb_headlen(skb) || + p_off = keys.control.thoff + thlen; + if (p_off > skb_headlen(skb) || keys.basic.ip_proto != ip_proto) return -EINVAL;
skb_set_transport_header(skb, keys.control.thoff); + } else if (gso_type) { + p_off = thlen; + if (p_off > skb_headlen(skb)) + return -EINVAL; } }
if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) { u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);
+ if (skb->len - p_off <= gso_size) + return -EINVAL; + skb_shinfo(skb)->gso_size = gso_size; skb_shinfo(skb)->gso_type = gso_type;