msgbufp=0xffffffff82521fe0 msg_size=1048544 msg_ptr=0xffffffff82422000
original: bufx=8735 bufr=0
setting geometry: bufx=1048544 (Vm=0), bufr=624272 (Vm=624272, > msg_size/2=524272)
verify: bufx=1048544 bufr=624272, n=424272, bug_len=4294767296 (underflow!)
sysctl rc=0, returned length l=424272 (msg_size=1048544)

NOTE: read returned 424272 bytes (< msg_size) -- bug is benign here.
restored bufx=8735 bufr=0