From 3aed194ac3edba9249b34fce09de36fa76326cbc Mon Sep 17 00:00:00 2001
From: usa <usa@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 27 Dec 2016 10:35:50 +0000
Subject: merge revision(s) 56938: [Backport #12988]

	Stop reading past the end of `ivptr` array

	If you have code like this:

	```ruby
	class A
  def initialize
    @a = nil
    @b = nil
    @c = nil
    @d = nil
    @e = nil
  end
	end

	x = A.new
	y = x.clone
	100.times { |z| x.instance_variable_set(:"@foo#{z}", nil) }
	puts y.inspect
	```

	`x` and `y` will share `iv_index_tbl` hashes.  However, the size of the
	hash will grow larger than the number if entries in `ivptr` in `y`.
	Before this commit, `rb_ivar_count` would use the size of the hash to
	determine how far to read in to the array, but this means that it could
	read past the end of the array and cause the program to segv

	[ruby-core:78403]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@57214 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 variable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'variable.c')

diff --git a/variable.c b/variable.c
index 691af04d3c..290a10b235 100644
--- a/variable.c
+++ b/variable.c
@@ -1322,7 +1322,7 @@ rb_ivar_count(VALUE obj)
     switch (BUILTIN_TYPE(obj)) {
       case T_OBJECT:
 	if ((tbl = ROBJECT_IV_INDEX_TBL(obj)) != 0) {
-	    st_index_t i, count, num = tbl->num_entries;
+	    st_index_t i, count, num = ROBJECT_NUMIV(obj);
 	    const VALUE *const ivptr = ROBJECT_IVPTR(obj);
 	    for (i = count = 0; i < num; ++i) {
 		if (ivptr[i] != Qundef) {
-- 
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