core, libctf: Check if constructor arguments are NULL before using them

  # pahole
  Segmentation fault (core dumped)
  #

Now we have:

  # ls -la bla
  ls: cannot access 'bla': No such file or directory
  # export PAHOLE_VMLINUX_BTF_FILENAME=bla
  # pahole
  pahole: couldn't find any debug information on this system.
  # pahole list_head
  pahole: couldn't find any debug information on this system.
  # pahole -F btf list_head
  pahole: couldn't find any btf debug information on this system.
  # pahole -F dwarf list_head
  pahole: couldn't find any dwarf debug information on this system.
  #

Reported-by: Matthias Schwarzott <[email protected]>
Reviewed-by: Alan Maguire <[email protected]>
Tested-by: Alan Maguire <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/all/ZzzY9uwdCO9hezd6@x1
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

dwarves.c

@@ -777,6 +777,9 @@ struct cu *cu__new(const char *name, uint8_t addr_size,
 		if (cu->use_obstack)
 			obstack_init(&cu->obstack);
 
+		if (name == NULL || filename == NULL)
+			goto out_free;
+
 		cu->name = strdup(name);
 		if (cu->name == NULL)
 			goto out_free;

libctf.c

@@ -179,6 +179,9 @@ struct ctf *ctf__new(const char *filename, Elf *elf)
 	struct ctf *ctf = zalloc(sizeof(*ctf));
 
 	if (ctf != NULL) {
+		if (filename == NULL)
+			goto out_delete;
+
 		ctf->filename = strdup(filename);
 		if (ctf->filename == NULL)
 			goto out_delete;