Unsigned integer wraparound in pcap-usb-linux-common.c:85:35

[kobrineli]

Hi! We've been fuzzing libpcap using sydr-fuzz and targets added to https://github.com/ispras/oss-sydr-fuzz/tree/master/projects/libpcap by @koltiradw. We've found unsigned integer wraparound error in pcap-usb-linux-common.c:85:35, but we don't know whether this is a real bug or a normal situation that is not worth to be reported.

Work environment

OS: Ubuntu 20.04
lipcap version: 53e9577

Bug description

Unsigned integer wraparound in pcap-usb-linux-common.c:85:35.

Steps to reproduce

1. Build docker container from https://github.com/ispras/oss-sydr-fuzz/tree/master/projects/libpcap:

    sudo docker build -t oss-sydr-fuzz-libpcap .
   

2. Run docker container:

    sudo docker run --privileged --network host -v /etc/localtime:/etc/localtime:ro --rm -it -v $PWD:/fuzz oss-sydr-fuzz-libpcap /bin/bash
   

3. Run sanitizer built target with the input leading to error (sydr_e669b5e526a19e08cb046f3f24413e3d13dc6860_int_overflow_0_unsigned.txt
   ):

    /libpcap/libfuzzer/fuzz_pcap sydr_e669b5e526a19e08cb046f3f24413e3d13dc6860_int_overflow_0_unsigned.txt
   

4. You will see the following output:

    INFO: Running with entropic power schedule (0xFF, 100).
    INFO: Seed: 2928156220
    INFO: Loaded 1 modules   (35773 inline 8-bit counters): 35773 [0x8c29e0, 0x8cb59d), 
    INFO: Loaded 1 PC tables (35773 PCs): 35773 [0x8cb5a0,0x957170), 
    /libpcap/libfuzzer/fuzz_pcap: Running 1 inputs 1 time(s) each.
    Running: /fuzz/pcap-out/security-unique/sydr_e669b5e526a19e08cb046f3f24413e3d13dc6860_int_overflow_0_unsigned
    ../pcap-usb-linux-common.c:85:35: runtime error: unsigned integer overflow: 1 + 4294967295 cannot be represented in type 'unsigned int'
    SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../pcap-usb-linux-common.c:85:35 in 
    ../pcap-usb-linux-common.c:95:24: runtime error: implicit conversion from type 'unsigned long' of value 8573157659 (64-bit, unsigned) to type 'u_int' (aka 'unsigned int') changed the value to 4278190363 (32-bit, unsigned)
    SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../pcap-usb-linux-common.c:95:24 in 
    Executed /fuzz/pcap-out/security-unique/sydr_e669b5e526a19e08cb046f3f24413e3d13dc6860_int_overflow_0_unsigned in 1 ms
    ***
    *** NOTE: fuzzing was not performed, you have only
    ***       executed the target code on a fixed set of inputs.
    ***