From 2b157688d19da5ce4fca6b5f3c78d2e309ecec9a Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Wed, 11 Nov 2020 18:36:36 +0530
Subject: [PATCH] hw/net/e1000e: advance desc_offset in case of null descriptor

While receiving packets via e1000e_write_packet_to_guest() routine,
'desc_offset' is advanced only when RX descriptor is processed. And
RX descriptor is not processed if it has NULL buffer address.
This may lead to an infinite loop condition. Increament 'desc_offset'
to process next descriptor in the ring to avoid infinite loop.

Reported-by: Cheol-woo Myung <330cjfdn@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry-picked from c2cb5116)
Fix CVE-2020-28916
Signed-off-by: Alex Chen <alex.chen@huawei.com>
---
 hw/net/e1000e_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c
index 2a221c2ef9..e45d47f584 100644
--- a/hw/net/e1000e_core.c
+++ b/hw/net/e1000e_core.c
@@ -1595,13 +1595,13 @@ e1000e_write_packet_to_guest(E1000ECore *core, struct NetRxPkt *pkt,
                           (const char *) &fcs_pad, e1000x_fcs_len(core->mac));
                 }
             }
-            desc_offset += desc_size;
-            if (desc_offset >= total_size) {
-                is_last = true;
-            }
         } else { /* as per intel docs; skip descriptors with null buf addr */
             trace_e1000e_rx_null_descriptor();
         }
+        desc_offset += desc_size;
+        if (desc_offset >= total_size) {
+            is_last = true;
+        }
 
         e1000e_write_rx_descr(core, desc, is_last ? core->rx_pkt : NULL,
                            rss_info, do_ps ? ps_hdr_len : 0, &bastate.written);
-- 
2.27.0