File 0380-slirp-check-pkt_len-before-reading-.patch of Package qemu.29142

From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Thu, 26 Nov 2020 19:27:06 +0530
Subject: slirp: check pkt_len before reading protocol header
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Git-commit: 2e1dcbc0c2af64fcb17009eaf2ceedd81be2b27f
References: 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>
[BR: no NCSI code, so only ARP patched]
---
 slirp/slirp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/slirp/slirp.c b/slirp/slirp.c
index 9f4bea3d3bf6765b81d1b317c9e1..da4c2eb6c2bb13c690538f4d7200 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -712,6 +712,10 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         return;
     }
 
+    if (pkt_len < ETH_HLEN + sizeof(struct arphdr)) {
+        return; /* packet too short */
+    }
+
     ar_op = ntohs(ah->ar_op);
     switch(ar_op) {
     case ARPOP_REQUEST: