QEMU: net: vmxnet: integer overflow may crash guest

[P J P]

* Gaoning Pan from Zhejiang University & Ant Security Light-Year Lab reported a malloc failure
  issue locates in vmxnet3_activate_device() of qemu/hw/net/vmxnet3.c NIC emulator

* This issue is reproducible because while activating the NIC device, vmxnet3_activate_device
  does not validate guest supplied configuration values against predefined min/max limits.

@@ -1420,6 +1420,7 @@ static void vmxnet3_activate_device(VMXNET3State *s)
     vmxnet3_setup_rx_filtering(s);
     /* Cache fields from shared memory */
     s->mtu = VMXNET3_READ_DRV_SHARED32(d, s->drv_shmem, devRead.misc.mtu);
+ assert(VMXNET3_MIN_MTU <= s->mtu && s->mtu < VMXNET3_MAX_MTU); <= Did not check if MTU is within range
     VMW_CFPRN("MTU is %u", s->mtu);

     s->max_rx_frags =
@@ -1473,6 +1474,9 @@ static void vmxnet3_activate_device(VMXNET3State *s)
         /* Read rings memory locations for TX queues */
         pa = VMXNET3_READ_TX_QUEUE_DESCR64(d, qdescr_pa, conf.txRingBasePA);
         size = VMXNET3_READ_TX_QUEUE_DESCR32(d, qdescr_pa, conf.txRingSize);
+ if (size > VMXNET3_TX_RING_MAX_SIZE) { <= Did not check TX ring size
+ size = VMXNET3_TX_RING_MAX_SIZE;
+ }

         vmxnet3_ring_init(d, &s->txq_descr[i].tx_ring, pa, size,
                           sizeof(struct Vmxnet3_TxDesc), false);
@@ -1483,6 +1487,9 @@ static void vmxnet3_activate_device(VMXNET3State *s)
         /* TXC ring */
         pa = VMXNET3_READ_TX_QUEUE_DESCR64(d, qdescr_pa, conf.compRingBasePA);
         size = VMXNET3_READ_TX_QUEUE_DESCR32(d, qdescr_pa, conf.compRingSize);
+ if (size > VMXNET3_TC_RING_MAX_SIZE) { <= Did not check TC ring size
+ size = VMXNET3_TC_RING_MAX_SIZE;
+ }
         vmxnet3_ring_init(d, &s->txq_descr[i].comp_ring, pa, size,
                           sizeof(struct Vmxnet3_TxCompDesc), true);
         VMXNET3_RING_DUMP(VMW_CFPRN, "TXC", i, &s->txq_descr[i].comp_ring);
@@ -1524,6 +1531,9 @@ static void vmxnet3_activate_device(VMXNET3State *s)
             /* RX rings */
             pa = VMXNET3_READ_RX_QUEUE_DESCR64(d, qd_pa, conf.rxRingBasePA[j]);
             size = VMXNET3_READ_RX_QUEUE_DESCR32(d, qd_pa, conf.rxRingSize[j]);
+ if (size > VMXNET3_RX_RING_MAX_SIZE) { <= Did not check RX ring size
+ size = VMXNET3_RX_RING_MAX_SIZE;
+ }
             vmxnet3_ring_init(d, &s->rxq_descr[i].rx_ring[j], pa, size,
                               sizeof(struct Vmxnet3_RxDesc), false);
             VMW_CFPRN("RX queue %d:%d: Base: %" PRIx64 ", Size: %d",
@@ -1533,6 +1543,9 @@ static void vmxnet3_activate_device(VMXNET3State *s)
         /* RXC ring */
         pa = VMXNET3_READ_RX_QUEUE_DESCR64(d, qd_pa, conf.compRingBasePA);
         size = VMXNET3_READ_RX_QUEUE_DESCR32(d, qd_pa, conf.compRingSize);
+ if (size > VMXNET3_RC_RING_MAX_SIZE) { <= Did not check RC ring size
+ size = VMXNET3_RC_RING_MAX_SIZE;
+ }

This may lead to potential integer overflow OR OOB buffer access issues.

[P J P (pjps)]

CVE-2021-20203 assigned by Red Hat Inc.

[Alexander Bulekov (a1xndr)]

Is this the same as https://bugs.launchpad.net/qemu/+bug/1890152 ?

[P J P (pjps)]

Yes, from the trace looks same.

[Thomas Huth (th-huth)]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/308