diff options
| author | Willem de Bruijn <willemb@google.com> | 2024-09-11 00:35:35 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2024-09-12 06:43:07 +0300 |
| commit | 6513eb3d3191574b58859ef2d6dc26c0277c6f81 (patch) | |
| tree | b1cd6c7569d52b6a54cca0b75546e75d4f8769b0 | |
| parent | 09a45a5553792bbf20beba0a1ac90b4692324d06 (diff) | |
| download | linux-6513eb3d3191574b58859ef2d6dc26c0277c6f81.tar.xz | |
net: tighten bad gso csum offset check in virtio_net_hdr
The referenced commit drops bad input, but has false positives.
Tighten the check to avoid these.
The check detects illegal checksum offload requests, which produce
csum_start/csum_off beyond end of packet after segmentation.
But it is based on two incorrect assumptions:
1. virtio_net_hdr_to_skb with VIRTIO_NET_HDR_GSO_TCP[46] implies GSO.
True in callers that inject into the tx path, such as tap.
But false in callers that inject into rx, like virtio-net.
Here, the flags indicate GRO, and CHECKSUM_UNNECESSARY or
CHECKSUM_NONE without VIRTIO_NET_HDR_F_NEEDS_CSUM is normal.
2. TSO requires checksum offload, i.e., ip_summed == CHECKSUM_PARTIAL.
False, as tcp[46]_gso_segment will fix up csum_start and offset for
all other ip_summed by calling __tcp_v4_send_check.
Because of 2, we can limit the scope of the fix to virtio_net_hdr
that do try to set these fields, with a bogus value.
Link: https://lore.kernel.org/netdev/20240909094527.GA3048202@port70.net/
Fixes: 89add40066f9 ("net: drop bad gso csum_start and offset in virtio_net_hdr")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20240910213553.839926-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | include/linux/virtio_net.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index 6c395a2600e8..276ca543ef44 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -173,7 +173,8 @@ retry: break; case SKB_GSO_TCPV4: case SKB_GSO_TCPV6: - if (skb->csum_offset != offsetof(struct tcphdr, check)) + if (skb->ip_summed == CHECKSUM_PARTIAL && + skb->csum_offset != offsetof(struct tcphdr, check)) return -EINVAL; break; } |