File 0220-e1000-fail-early-for-evil-descripto.patch of Package qemu.20395

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File 0220-e1000-fail-early-for-evil-descripto.patch of Package qemu.20395

From: Jason Wang <jasowang@redhat.com>
Date: Wed, 24 Feb 2021 13:45:28 +0800
Subject: 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>
---
 hw/net/e1000.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/net/e1000.c b/hw/net/e1000.c
index 05a00cba31b7b53ff7c15e288d9b..c5d60d61540e1b1a4a4492b2e92d 100644
--- a/hw/net/e1000.c
+++ b/hw/net/e1000.c
@@ -647,6 +647,9 @@ process_tx_desc(E1000State *s, struct e1000_tx_desc *dp)
         msh = tp->props.hdr_len + tp->props.mss;
         do {
             bytes = split_size;
+            if (tp->size >= msh) {
+                goto eop;
+            }
             if (tp->size + bytes > msh)
                 bytes = msh - tp->size;
 
@@ -674,6 +677,7 @@ 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->props.tse && tp->props.cptse && tp->size < tp->props.hdr_len)) {

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File 0220-e1000-fail-early-for-evil-descripto.patch of Package qemu.20395

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