File hw-net-xgmac-Fix-buffer-overflow-in-xgma.patch of Package qemu.19783

From: Mauro Matteo Cascella <mcascell@redhat.com>
Date: Fri, 10 Jul 2020 11:19:41 +0200
Subject: hw/net/xgmac: Fix buffer overflow in xgmac_enet_send()

Git-commit: 5519724a13664b43e225ca05351c60b4468e4555
References: bsc#1174386 CVE-2020-15863

A buffer overflow issue was reported by Mr. Ziming Zhang, CC'd here. It
occurs while sending an Ethernet frame due to missing break statements
and improper checking of the buffer size.

Reported-by: Ziming Zhang <ezrakiez@gmail.com>
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 hw/net/xgmac.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/hw/net/xgmac.c b/hw/net/xgmac.c
index 2ea8d2ec721632ecd13026eedf03..3b02b38f4e7ac9da650a6a02633d 100644
--- a/hw/net/xgmac.c
+++ b/hw/net/xgmac.c
@@ -220,21 +220,31 @@ static void xgmac_enet_send(XgmacState *s)
         }
         len = (bd.buffer1_size & 0xfff) + (bd.buffer2_size & 0xfff);
 
+        /*
+         * FIXME: these cases of malformed tx descriptors (bad sizes)
+         * should probably be reported back to the guest somehow
+         * rather than simply silently stopping processing, but we
+         * don't know what the hardware does in this situation.
+         * This will only happen for buggy guests anyway.
+         */
         if ((bd.buffer1_size & 0xfff) > 2048) {
             DEBUGF_BRK("qemu:%s:ERROR...ERROR...ERROR... -- "
                         "xgmac buffer 1 len on send > 2048 (0x%x)\n",
                          __func__, bd.buffer1_size & 0xfff);
+            break;
         }
         if ((bd.buffer2_size & 0xfff) != 0) {
             DEBUGF_BRK("qemu:%s:ERROR...ERROR...ERROR... -- "
                         "xgmac buffer 2 len on send != 0 (0x%x)\n",
                         __func__, bd.buffer2_size & 0xfff);
+            break;
         }
-        if (len >= sizeof(frame)) {
+        if (frame_size + len >= sizeof(frame)) {
             DEBUGF_BRK("qemu:%s: buffer overflow %d read into %zu "
-                        "buffer\n" , __func__, len, sizeof(frame));
+                        "buffer\n" , __func__, frame_size + len, sizeof(frame));
             DEBUGF_BRK("qemu:%s: buffer1.size=%d; buffer2.size=%d\n",
                         __func__, bd.buffer1_size, bd.buffer2_size);
+            break;
         }
 
         cpu_physical_memory_read(bd.buffer1_addr, ptr, len);