From d48034cc2b331313995c1d19060decc0e5ca1356 Mon Sep 17 00:00:00 2001
From: Jon Maloy <jmaloy@redhat.com>
Date: Thu, 14 Jan 2021 01:35:41 -0500
Subject: [PATCH 17/17] hw/net/e1000e: advance desc_offset in case of null
 descriptor
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RH-Author: Jon Maloy <jmaloy@redhat.com>
Message-id: <20210114013541.956735-2-jmaloy@redhat.com>
Patchwork-id: 100638
O-Subject: [RHEL-8.4.0 qemu-kvm PATCH 1/1] hw/net/e1000e: advance desc_offset in case of null descriptor
Bugzilla: 1903070
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>

From: Prasad J Pandit <pjp@fedoraproject.org>

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 c2cb511634012344e3d0fe49a037a33b12d8a98a)
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.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 9b76f82db5b..166054f2e3f 100644
--- a/hw/net/e1000e_core.c
+++ b/hw/net/e1000e_core.c
@@ -1596,13 +1596,13 @@ 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