bpftool: fix potential NULL pointer dereferencing in prog_dump()

A NULL pointer dereference could occur if ksyms
is not properly checked before usage in the prog_dump() function.

Fixes: b053b439b72a ("bpf: libbpf: bpftool: Print bpf_line_info during prog dump")
Signed-off-by: Amir Mohammadi <[email protected]>
Reviewed-by: Quentin Monnet <[email protected]>
Acked-by: John Fastabend <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: amiremohamadi

src/prog.c

@@ -822,11 +822,18 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
 					printf("%s:\n", sym_name);
 				}
 
-				if (disasm_print_insn(img, lens[i], opcodes,
-						      name, disasm_opt, btf,
-						      prog_linfo, ksyms[i], i,
-						      linum))
-					goto exit_free;
+				if (ksyms) {
+					if (disasm_print_insn(img, lens[i], opcodes,
+							      name, disasm_opt, btf,
+							      prog_linfo, ksyms[i], i,
+							      linum))
+						goto exit_free;
+				} else {
+					if (disasm_print_insn(img, lens[i], opcodes,
+							      name, disasm_opt, btf,
+							      NULL, 0, 0, false))
+						goto exit_free;
+				}
 
 				img += lens[i];