Fix CVE-2019-12067
AHCI emulator while committing DMA buffer in ahci_commit_buf()
may do a NULL dereference if the command header 'ad->cur_cmd'
is null. Add check to avoid it.
Reported-by: Bugs SysSec <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
Signed-off-by: Jiajie Li <lijiajie11@huawei.com>
