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authorWillem de Bruijn <willemb@google.com>2019-02-15 12:15:47 -0500
committerDavid S. Miller <davem@davemloft.net>2019-02-15 20:30:37 -0800
commitd5be7f632bad0f489879eed0ff4b99bd7fe0b74c (patch)
tree611f6b5968dbaed249619d63ec6e060ad10d33c6 /include
parent3b89ea9c5902acccdbbdec307c85edd1bf52515e (diff)
net: validate untrusted gso packets without csum offload
Syzkaller again found a path to a kernel crash through bad gso input. By building an excessively large packet to cause an skb field to wrap. If VIRTIO_NET_HDR_F_NEEDS_CSUM was set this would have been dropped in skb_partial_csum_set. GSO packets that do not set checksum offload are suspicious and rare. Most callers of virtio_net_hdr_to_skb already pass them to skb_probe_transport_header. Move that test forward, change it to detect parse failure and drop packets on failure as those cleary are not one of the legitimate VIRTIO_NET_HDR_GSO types. Fixes: bfd5f4a3d605 ("packet: Add GSO/csum offload support.") Fixes: f43798c27684 ("tun: Allow GSO using virtio_net_hdr") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Willem de Bruijn <willemb@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/linux/skbuff.h2
-rw-r--r--include/linux/virtio_net.h9
2 files changed, 10 insertions, 1 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 95d25b010a25..4c1c82a5678c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2434,7 +2434,7 @@ static inline void skb_probe_transport_header(struct sk_buff *skb,
if (skb_flow_dissect_flow_keys_basic(skb, &keys, NULL, 0, 0, 0, 0))
skb_set_transport_header(skb, keys.control.thoff);
- else
+ else if (offset_hint >= 0)
skb_set_transport_header(skb, offset_hint);
}
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index cb462f9ab7dd..71f2394abbf7 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -57,6 +57,15 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
if (!skb_partial_csum_set(skb, start, off))
return -EINVAL;
+ } else {
+ /* gso packets without NEEDS_CSUM do not set transport_offset.
+ * probe and drop if does not match one of the above types.
+ */
+ if (gso_type) {
+ skb_probe_transport_header(skb, -1);
+ if (!skb_transport_header_was_set(skb))
+ return -EINVAL;
+ }
}
if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {