From edc243851279e3393000b28b6b69454cae1190ef Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Fri, 11 Apr 2014 15:18:08 +0300 Subject: [PATCH] virtio-net: fix guest-triggerable buffer overrun Bug-Debian: http://bugs.debian.org/744221 When VM guest programs multicast addresses for a virtio net card, it supplies a 32 bit entries counter for the number of addresses. These addresses are read into tail portion of a fixed macs array which has size MAC_TABLE_ENTRIES, at offset equal to in_use. To avoid overflow of this array by guest, qemu attempts to test the size as follows: - if (in_use + mac_data.entries <= MAC_TABLE_ENTRIES) { however, as mac_data.entries is uint32_t, this sum can overflow, e.g. if in_use is 1 and mac_data.entries is 0xffffffff then in_use + mac_data.entries will be 0. Qemu will then read guest supplied buffer into this memory, overflowing buffer on heap. CVE-2014-0150 Cc: qemu-stable@nongnu.org Signed-off-by: Michael S. Tsirkin Message-id: 1397218574-25058-1-git-send-email-mst@redhat.com Reviewed-by: Michael Tokarev Signed-off-by: Peter Maydell Backported-to-1.1: Michael Tokarev --- hw/net/virtio-net.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -366,7 +366,7 @@ static int virtio_net_handle_mac(VirtION return VIRTIO_NET_ERR; if (mac_data.entries) { - if (n->mac_table.in_use + mac_data.entries <= MAC_TABLE_ENTRIES) { + if (mac_data.entries <= MAC_TABLE_ENTRIES - n->mac_table.in_use) { memcpy(n->mac_table.macs + (n->mac_table.in_use * ETH_ALEN), elem->out_sg[2].iov_base + sizeof(mac_data), mac_data.entries * ETH_ALEN);