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 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 --- hw/net/virtio-net.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 439477b954..33bd233a2d 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -677,7 +677,7 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd, goto error; } - if (in_use + mac_data.entries <= MAC_TABLE_ENTRIES) { + if (mac_data.entries <= MAC_TABLE_ENTRIES - in_use) { s = iov_to_buf(iov, iov_cnt, 0, &macs[in_use * ETH_ALEN], mac_data.entries * ETH_ALEN); if (s != mac_data.entries * ETH_ALEN) {