NULL pointer dereference in cbor_typeof

[gy741]

Hello.

I found a NULL pointer dereference in libcbor.

Please confirm.

Thanks.

Summary: NULL pointer dereference
OS: CentOS 7 64bit
Version: commit f4ec5a4
PoC Download: crash.zip

Steps to reproduce:
1.Download the .POC files.
2.Compile the source code with ASan.
3.Execute the following command
: ./readfile $POC

ASAN:DEADLYSIGNAL
=================================================================
==31346==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000020 (pc 0x0000004f32d7 bp 0x7ffe7ef988f0 sp 0x7ffe7ef988d0 T0)
==31346==The signal is caused by a READ memory access.
==31346==Hint: address points to the zero page.
    #0 0x4f32d6 in cbor_typeof /home/karas/libcbor/src/cbor/common.c:61:15
    #1 0x4e9683 in _cbor_nested_describe /home/karas/libcbor/src/cbor.c:260:10
    #2 0x4e9df8 in _cbor_nested_describe /home/karas/libcbor/src/cbor.c:353:4
    #3 0x4e963e in cbor_describe /home/karas/libcbor/src/cbor.c:388:2
    #4 0x4e7d5d in main /home/karas/libcbor/examples/readfile.c:77:2
    #5 0x7fdca2c113f0 in __libc_start_main /build/glibc-mXZSwJ/glibc-2.24/csu/../csu/libc-start.c:291
    #6 0x41ba09 in _start (/home/karas/libcbor/examples/readfile+0x41ba09)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /home/karas/libcbor/src/cbor/common.c:61:15 in cbor_typeof
==31346==ABORTING

================
[Acknowledgement]
This work was supported by ICT R&D program of MSIP/IITP. [R7518-16-1001, Innovation hub for high Performance Computing]