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ruby--ruby/internal/symbol.h
Daniel Colson 32e406d6d3 Ensure _id2ref finds symbols with the correct type
Prior to this commit it was possible to call `ObjectSpace._id2ref` with
an offset static symbol object_id and get back a new, incorrectly tagged
symbol:

```
> sensible_sym = ObjectSpace._id2ref(:a.object_id)
=> :a
> nonsense_sym = ObjectSpace._id2ref(:a.object_id + 40)
=> :a
> sensible_sym == nonsense_sym
=> false
```

`nonsense_sym` ends up tagged with `RUBY_ID_INSTANCE` instead of
`RB_ID_LOCAL`. That means we can do silly things like:

```
> foo = Object.new
> foo.instance_variable_set(:a, 123)
(irb):2:in `instance_variable_set': `a' is not allowed as an instance variable name (NameError)
> foo.instance_variable_set(ObjectSpace._id2ref(:a.object_id + 40), 123)
=> 123
> foo.instance_variables
=> [:a]
```

This was happening because `get_id_entry` ignores the tag bits when
looking up the symbol. So `rb_id2str(symid)` would return a value and
then we'd continue on with the nonsense `symid`.

This commit prevents the situation by checking that the `symid` actually
matches what we get back from `get_id_entry`. Now we get a `RangeError`
for the nonsense id:

```
> ObjectSpace._id2ref(:a.object_id)
=> :a
> ObjectSpace._id2ref(:a.object_id + 40)
(irb):1:in `_id2ref': 0x000000000013f408 is not symbol id value (RangeError)
```

Co-authored-by: John Hawthorn <jhawthorn@github.com>
2022-07-20 10:38:44 -07:00

42 lines
1.5 KiB
C

#ifndef INTERNAL_SYMBOL_H /*-*-C-*-vi:se ft=c:*/
#define INTERNAL_SYMBOL_H
/**
* @author Ruby developers <ruby-core@ruby-lang.org>
* @copyright This file is a part of the programming language Ruby.
* Permission is hereby granted, to either redistribute and/or
* modify this file, provided that the conditions mentioned in the
* file COPYING are met. Consult the file for details.
* @brief Internal header for Symbol.
*/
#include "ruby/ruby.h" /* for VALUE */
#include "ruby/encoding.h" /* for rb_encoding */
#include "internal/compilers.h" /* for __has_builtin */
#ifdef rb_sym_intern_ascii_cstr
# undef rb_sym_intern_ascii_cstr
#endif
/* symbol.c */
VALUE rb_to_symbol_type(VALUE obj);
VALUE rb_sym_intern(const char *ptr, long len, rb_encoding *enc);
VALUE rb_sym_intern_ascii(const char *ptr, long len);
VALUE rb_sym_intern_ascii_cstr(const char *ptr);
int rb_is_const_name(VALUE name);
int rb_is_class_name(VALUE name);
int rb_is_instance_name(VALUE name);
int rb_is_local_name(VALUE name);
PUREFUNC(int rb_is_const_sym(VALUE sym));
PUREFUNC(int rb_is_attrset_sym(VALUE sym));
ID rb_make_internal_id(void);
ID rb_make_temporary_id(size_t n);
void rb_gc_free_dsymbol(VALUE);
int rb_static_id_valid_p(ID id);
#if __has_builtin(__builtin_constant_p)
#define rb_sym_intern_ascii_cstr(ptr) \
(__builtin_constant_p(ptr) ? \
rb_sym_intern_ascii((ptr), (long)strlen(ptr)) : \
rb_sym_intern_ascii_cstr(ptr))
#endif
#endif /* INTERNAL_SYMBOL_H */