From c2df0d478b2605da10363ab57825cdbc34caa680 Mon Sep 17 00:00:00 2001
From: Alex Chen <alex.chen@huawei.com>
Date: Mon, 14 Dec 2020 15:39:46 +0800
Subject: [PATCH] slirp: check pkt_len before reading protocol header
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While processing ARP/NCSI packets in 'arp_input' or 'ncsi_input'
routines, ensure that pkt_len is large enough to accommodate the
respective protocol headers, lest it should do an OOB access.
Add check to avoid it.

CVE-2020-29129 CVE-2020-29130
  QEMU: slirp: out-of-bounds access while processing ARP/NCSI packets
 -> https://www.openwall.com/lists/oss-security/2020/11/27/1

Reported-by: Qiuhao Li <Qiuhao.Li@outlook.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-Id: <20201126135706.273950-1-ppandit@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
(cherry-picked from 2e1dcbc0)
Signed-off-by: Alex Chen <alex.chen@huawei.com>
---
 slirp/src/ncsi.c  | 4 ++++
 slirp/src/slirp.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/slirp/src/ncsi.c b/slirp/src/ncsi.c
index 6864b735..251c0d2b 100644
--- a/slirp/src/ncsi.c
+++ b/slirp/src/ncsi.c
@@ -147,6 +147,10 @@ void ncsi_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
     uint32_t checksum;
     uint32_t *pchecksum;
 
+    if (pkt_len < ETH_HLEN + sizeof(struct ncsi_pkt_hdr)) {
+        return; /* packet too short */
+    }
+
     memset(ncsi_reply, 0, sizeof(ncsi_reply));
 
     memset(reh->h_dest, 0xff, ETH_ALEN);
diff --git a/slirp/src/slirp.c b/slirp/src/slirp.c
index b0194cb3..86b0f52d 100644
--- a/slirp/src/slirp.c
+++ b/slirp/src/slirp.c
@@ -700,6 +700,10 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         return;
     }
 
+    if (pkt_len < ETH_HLEN + sizeof(struct slirp_arphdr)) {
+        return; /* packet too short */
+    }
+
     ar_op = ntohs(ah->ar_op);
     switch (ar_op) {
     case ARPOP_REQUEST:
-- 
2.23.0