Error write dump Mifare 4k

[GiorgioRoma]

When i used mfoc to read dump of mifare classic 4k, read all 256 block, but don't write dump.
The error is: Error, cannot write dump

[gudata]

check free space disk :)

[GiorgioRoma]

:-) no no, the disk is empty.....
I use mfoc with Kali Linux that run on Virtual box (the real os is OSX 10.12.4).
Mfoc, reads and writes correctly the 1k mifare, but does not write on the mifare 4k.
This is the code that generates the error (I think there is a problem with the dump size check):

// Finally save all keys + data to file uint16_t dump_size = (t.num_blocks + 1) * 16; if (fwrite(&mtDump, 1, dump_size, pfDump) != dump_size) { fprintf(stdout, "Error, cannot write dump\n"); fclose(pfDump); goto error; } fclose(pfDump);

(I'm trying to use mfoc directly from mac, but i have another error):

mfoc -O tes.mfd
error libnfc.driver.acr122_usb Unable to claim USB interface (Permission denied)
No NFC device found.

nfc-list
nfc-list uses libnfc 1.7.1
error libnfc.driver.acr122_usb Unable to claim USB interface (Permission denied)
nfc-list: ERROR: Unable to open NFC device: acr122_usb:020:012
NFC device: ACS ACR122U / ACR122U214 opened
1 ISO14443A passive target(s) found:
ISO/IEC 14443A (106 kbps) target:
ATQA (SENS_RES): xx xx
UID (NFCID1): xx xx xx xx
SAK (SEL_RES): xx

[GiorgioRoma]

Update:
I managed to use mfoc from mac osx, no dump writing error even with 4k mifare.