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e1000: fail early for evil descriptor
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>
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jasowang committed Mar 15, 2021
1 parent e73b431 commit 3de46e6
Showing 1 changed file with 4 additions and 0 deletions.
4 changes: 4 additions & 0 deletions hw/net/e1000.c
Expand Up @@ -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;

Expand All @@ -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)) {
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