work_around_broken_dhclient() accesses IP and UDP headers to detect relevant packets and to calculate checksums, but it didn't check if the packet has size sufficient to accommodate them, causing out-of-bound access hazards. Fix this by correcting the size requirement.
Fixes: 1d41b0c1ec66 ("Work around dhclient brokenness") Cc: qemu-sta...@nongnu.org Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com> Signed-off-by: Jason Wang <jasow...@redhat.com> (cherry picked from commit a8575f7fb2f213e6690b23160b04271d47fdfaa8) Signed-off-by: Michael Tokarev <m...@tls.msk.ru> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index ed33a32877..cf27d5cbe5 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -1692,8 +1692,11 @@ static void virtio_net_hdr_swap(VirtIODevice *vdev, struct virtio_net_hdr *hdr) static void work_around_broken_dhclient(struct virtio_net_hdr *hdr, uint8_t *buf, size_t size) { + size_t csum_size = ETH_HLEN + sizeof(struct ip_header) + + sizeof(struct udp_header); + if ((hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && /* missing csum */ - (size > 27 && size < 1500) && /* normal sized MTU */ + (size >= csum_size && size < 1500) && /* normal sized MTU */ (buf[12] == 0x08 && buf[13] == 0x00) && /* ethertype == IPv4 */ (buf[23] == 17) && /* ip.protocol == UDP */ (buf[34] == 0 && buf[35] == 67)) { /* udp.srcport == bootps */ -- 2.39.5