Null pointer dereferencing in bpf_object__collect_prog_relos

[rish9101]

I found a null pointer dereferencing bug at line 4268 in libbpf.c. This is caused due to a accessing a pointer of type Elf_Data being NULL. This holds the section data in the function and no check for it being NULL is present in bpf_object__collect_prog_relos function.
The bug is triggered by fuzzing using the harness bpf-object-fuzzer.c provided in fuzz folder.
The stack trace is attached below

#0  0x0000000000408764 in bpf_object__collect_prog_relos (obj=<optimized out>, shdr=<optimized out>, data=<optimized out>) at libbpf.c:4268
#1  bpf_object__collect_relos (obj=<optimized out>) at libbpf.c:6696
#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:7380
#3  0x0000000000409bdb in bpf_object__open_mem (obj_buf=0x44b8c8, obj_buf_sz=0x15, opts=0x7) 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_deref_2.zip