slirp: update to fix CVE-2020-29129 CVE-2020-29130

slirp: update to fix CVE-2020-29129 CVE-2020-29130

An out-of-bounds access issue was found in the SLIRP user networking
implementation of QEMU. It could occur while processing ARP/NCSI
packets, if the packet length was shorter than required to accommodate
respective protocol headers and payload. A privileged guest user may use
this flaw to potentially leak host information bytes.

Marc-André Lureau (1):
      Merge branch 'stable-4.2' into 'stable-4.2'

Prasad J Pandit (1):
      slirp: check pkt_len before reading protocol header

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>