Headline
CVE-2021-20257: [PATCH] e1000: fail early for evil descriptor
An infinite loop flaw was found in the e1000 NIC emulator of the QEMU. This issue occurs while processing transmits (tx) descriptors in process_tx_desc if various descriptor fields are initialized with invalid values. This flaw allows a guest to consume CPU cycles on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.
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From:
Jason Wang
Subject:
[PATCH] e1000: fail early for evil descriptor
Date:
Wed, 24 Feb 2021 13:45:28 +0800
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 [email protected] Reported-by: Cheolwoo Myung [email protected] Reported-by: Ruhr-University Bochum [email protected] Cc: Prasad J Pandit [email protected] Signed-off-by: Jason Wang [email protected]
hw/net/e1000.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/hw/net/e1000.c b/hw/net/e1000.c index d8da2f6528…4345d863e6 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)) { – 2.25.1
[PATCH] e1000: fail early for evil descriptor, Jason Wang <=
- Re: [PATCH] e1000: fail early for evil descriptor, Jason Wang, 2021/02/26
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