From: Jason Wang <jasowang@redhat.com>
Date: Wed, 24 Feb 2021 05:45:28 +0000 (+0800)
Subject: e1000: fail early for evil descriptor
X-Git-Tag: upstream/5.2.0~107
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=147cb10b23d842d3504c15046e8ec9ee524d0936;p=platform%2Fupstream%2Fqemu.git

e1000: fail early for evil descriptor

Git-commit: 3de46e6fc489c52c9431a8a832ad8170a7569bd8
References: bsc#1182577, CVE-2021-20257

During procss_tx_desc(), driver can try to chain data descriptor with
legacy descriptor, when will lead underflow for the following
calculation in process_tx_desc() for bytes:

            if (tp->size + bytes > msh)
                bytes = msh - tp->size;

This will lead a infinite loop. So check and fail early if tp->size if
greater or equal to msh.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Reported-by: Cheolwoo Myung <cwmyung@snu.ac.kr>
Reported-by: Ruhr-University Bochum <bugs-syssec@rub.de>
Cc: Prasad J Pandit <ppandit@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Bruce Rogers <brogers@suse.com>
---

diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index d7d05ae..02a446b 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -670,6 +670,9 @@ process_tx_desc(E1000State *s, struct e1000_tx_desc *dp)
         msh = tp->tso_props.hdr_len + tp->tso_props.mss;
         do {
             bytes = split_size;
+            if (tp->size >= msh) {
+                goto eop;
+            }
             if (tp->size + bytes > msh)
                 bytes = msh - tp->size;
 
@@ -695,6 +698,7 @@ process_tx_desc(E1000State *s, struct e1000_tx_desc *dp)
         tp->size += split_size;
     }
 
+eop:
     if (!(txd_lower & E1000_TXD_CMD_EOP))
         return;
     if (!(tp->cptse && tp->size < tp->tso_props.hdr_len)) {