The tulip networking card emulation has an OOB issue in
'tulip_copy_tx_buffers' when the guest provide malformed descriptor.
This test will trigger a ASAN heap overflow crash. To trigger this
issue we can construct the data as following:

1. construct a 'tulip_descriptor'. Its control is set to
'0x7ff | 0x7ff << 11', this will make the 'tulip_copy_tx_buffers's
'len1' and 'len2' to 0x7ff(2047). So 'len1+len2' will overflow
'TULIPState's 'tx_frame' field. This descriptor's 'buf_addr1' and
'buf_addr2' should set to a guest address.

2. write this descriptor to tulip device's CSR4 register. This will
set the 'TULIPState's 'current_tx_desc' field.

3. write 'CSR6_ST' to tulip device's CSR6 register. This will trigger
'tulip_xmit_list_update' and finally calls 'tulip_copy_tx_buffers'.

Following shows the backtrack of crash:

==31781==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x628000007cd0 at pc 0x7fe03c5a077a bp 0x7fff05b46770 sp 0x7fff05b45f18
WRITE of size 2047 at 0x628000007cd0 thread T0
    #0 0x7fe03c5a0779  (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x79779)
    #1 0x5575fb6daa6a in flatview_read_continue /home/test/qemu/exec.c:3194
    #2 0x5575fb6daccb in flatview_read /home/test/qemu/exec.c:3227
    #3 0x5575fb6dae66 in address_space_read_full /home/test/qemu/exec.c:3240
    #4 0x5575fb6db0cb in address_space_rw /home/test/qemu/exec.c:3268
    #5 0x5575fbdfd460 in dma_memory_rw_relaxed /home/test/qemu/include/sysemu/dma.h:87
    #6 0x5575fbdfd4b5 in dma_memory_rw /home/test/qemu/include/sysemu/dma.h:110
    #7 0x5575fbdfd866 in pci_dma_rw /home/test/qemu/include/hw/pci/pci.h:787
    #8 0x5575fbdfd8a3 in pci_dma_read /home/test/qemu/include/hw/pci/pci.h:794
    #9 0x5575fbe02761 in tulip_copy_tx_buffers hw/net/tulip.c:585
    #10 0x5575fbe0366b in tulip_xmit_list_update hw/net/tulip.c:678
    #11 0x5575fbe04073 in tulip_write hw/net/tulip.c:783

Signed-off-by: Li Qiang <liq3ea@163.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>