From fa1aaeeab2f10d7f107dd45a2c06e40e71bde1c3 Mon Sep 17 00:00:00 2001 From: "wexu@redhat.com" Date: Wed, 21 Dec 2016 06:04:24 +0100 Subject: [PATCH 3/4] net: check packet payload length RH-Author: wexu@redhat.com Message-id: <1482300264-29708-2-git-send-email-wexu@redhat.com> Patchwork-id: 73088 O-Subject: [RHEL-7.4/7.3.z qemu-kvm Patch v2] net: check packet payload length Bugzilla: 1398218 RH-Acked-by: Laurent Vivier RH-Acked-by: Michael S. Tsirkin RH-Acked-by: Stefan Hajnoczi From: Prasad J Pandit While computing IP checksum, 'net_checksum_calculate' reads payload length from the packet. It could exceed the given 'data' buffer size. Add a check to avoid it. This patch is to fix CVE-2016-2857. https://access.redhat.com/security/cve/CVE-2016-2857 Reported-by: Liu Ling Signed-off-by: Prasad J Pandit Signed-off-by: Jason Wang (cherry picked from commit 362786f14a753d8a5256ef97d7c10ed576d6572b) Signed-off-by: Wei Xu Signed-off-by: Miroslav Rezanina --- net/checksum.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/net/checksum.c b/net/checksum.c index 14c0855..0942437 100644 --- a/net/checksum.c +++ b/net/checksum.c @@ -59,6 +59,11 @@ void net_checksum_calculate(uint8_t *data, int length) int hlen, plen, proto, csum_offset; uint16_t csum; + /* Ensure data has complete L2 & L3 headers. */ + if (length < 14 + 20) { + return; + } + if ((data[14] & 0xf0) != 0x40) return; /* not IPv4 */ hlen = (data[14] & 0x0f) * 4; @@ -76,8 +81,9 @@ void net_checksum_calculate(uint8_t *data, int length) return; } - if (plen < csum_offset+2) - return; + if (plen < csum_offset + 2 || 14 + hlen + plen > length) { + return; + } data[14+hlen+csum_offset] = 0; data[14+hlen+csum_offset+1] = 0; -- 1.8.3.1