slirp: check pkt_len before reading protocol header

Git-commit: 2e1dcbc0c2af64fcb17009eaf2ceedd81be2b27f
References: bsc#1179466, bsc#1179467

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>
Signed-off-by: Bruce Rogers <brogers@suse.com>

diff --git a/slirp/src/ncsi.c b/slirp/src/ncsi.c
index ddd980d869546d314df6f6441475b7831e773fc7..4bc1d07faadc94ec578d51e58c2ca95680e1909a 100644 (file)
--- 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 14458e8510e7ca2d7045770305245e4743991867..ef359c862b34c75bf5454320c5d17659a6e3f522 100644 (file)
--- a/slirp/src/slirp.c
+++ b/slirp/src/slirp.c
@@ -755,6 +755,10 @@ 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: