From: Willem de Bruijn willemb@google.com
[ Upstream commit fc8b2a619469378717e7270d2a4e1ef93c585f7a ]
Syzbot reported two new paths to hit an internal WARNING using the new virtio gso type VIRTIO_NET_HDR_GSO_UDP_L4.
RIP: 0010:skb_checksum_help+0x4a2/0x600 net/core/dev.c:3260 skb len=64521 gso_size=344 and
RIP: 0010:skb_warn_bad_offload+0x118/0x240 net/core/dev.c:3262
Older virtio types have historically had loose restrictions, leading to many entirely impractical fuzzer generated packets causing problems deep in the kernel stack. Ideally, we would have had strict validation for all types from the start.
New virtio types can have tighter validation. Limit UDP GSO packets inserted via virtio to the same limits imposed by the UDP_SEGMENT socket interface:
1. must use checksum offload 2. checksum offload matches UDP header 3. no more segments than UDP_MAX_SEGMENTS 4. UDP GSO does not take modifier flags, notably SKB_GSO_TCP_ECN
Fixes: 860b7f27b8f7 ("linux/virtio_net.h: Support USO offload in vnet header.") Reported-by: syzbot+01cdbc31e9c0ae9b33ac@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/0000000000005039270605eb0b7f@google.com/ Reported-by: syzbot+c99d835ff081ca30f986@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/0000000000005426680605eb0b9f@google.com/ Signed-off-by: Willem de Bruijn willemb@google.com Reviewed-by: Eric Dumazet edumazet@google.com Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: David S. Miller davem@davemloft.net
[5.15 stable: clean backport] Signed-off-by: Willem de Bruijn willemb@google.com --- include/linux/virtio_net.h | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index 29b19d0a324c7..137357fb6a574 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -3,8 +3,8 @@ #define _LINUX_VIRTIO_NET_H
#include <linux/if_vlan.h> +#include <linux/udp.h> #include <uapi/linux/tcp.h> -#include <uapi/linux/udp.h> #include <uapi/linux/virtio_net.h>
static inline bool virtio_net_hdr_match_proto(__be16 protocol, __u8 gso_type) @@ -155,9 +155,22 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, unsigned int nh_off = p_off; struct skb_shared_info *shinfo = skb_shinfo(skb);
- /* UFO may not include transport header in gso_size. */ - if (gso_type & SKB_GSO_UDP) + switch (gso_type & ~SKB_GSO_TCP_ECN) { + case SKB_GSO_UDP: + /* UFO may not include transport header in gso_size. */ nh_off -= thlen; + break; + case SKB_GSO_UDP_L4: + if (!(hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM)) + return -EINVAL; + if (skb->csum_offset != offsetof(struct udphdr, check)) + return -EINVAL; + if (skb->len - p_off > gso_size * UDP_MAX_SEGMENTS) + return -EINVAL; + if (gso_type != SKB_GSO_UDP_L4) + return -EINVAL; + break; + }
/* Kernel has a special handling for GSO_BY_FRAGS. */ if (gso_size == GSO_BY_FRAGS)