Null pointer dereferencing in bpf_object__collect_externs

[rish9101]

I found a null pointer dereferencing bug at line 3828 of libbpf.c. This is caused due to one of the arguments to strcmp being a NULL Pointer.
The bug is triggered by fuzzing using the harness bpf-object-fuzzer.c provided in fuzz folder.

The stack trace of the execution is

#0  __strcmp_avx2 () at ../sysdeps/x86_64/multiarch/strcmp-avx2.S:101
#1  0x000000000040606b in bpf_object__collect_externs (obj=<optimized out>) at libbpf.c:3828
#2  bpf_object_open (path=<optimized out>, path@entry=0x0, obj_buf=<optimized out>, obj_buf_sz=<optimized out>, opts=<optimized out>) at libbpf.c:7376
#3  0x0000000000409bdb in bpf_object__open_mem (obj_buf=0x4372f5, obj_buf_sz=0x0, opts=0x0) at libbpf.c:7415

The crashing input has been attached below.

The bug has been tested on Ubuntu 20.04, libbpf built with clang-11.

null_ptr_strcmp_2.zip