From f3abe5ba645839fb2a686aee18d3466b59256af0 Mon Sep 17 00:00:00 2001
From: "NARUSE, Yui" <naruse@airemix.jp>
Date: Fri, 17 Mar 2023 13:40:04 +0900
Subject: merge revision(s)
 0700d0fd1c77b4fddf803dea3c10be654df600ff,62c2082f1f726cb90d8c332fbedbecf41d5d82ec:
 [Backport #19469]

	Fix indentation in vm_setivar_default

	---
	 vm_insnhelper.c | 6 +++---
	 1 file changed, 3 insertions(+), 3 deletions(-)

	[Bug #19469] Fix crash when resizing generic iv list

	The following script can sometimes trigger a crash:

	```ruby
	GC.stress = true

	class Array
	  def foo(bool)
	    if bool
	      @a = 1
	      @b = 2
	      @c = 1
	    else
	      @c = 1
	    end
	  end
	end

	obj = []
	obj.foo(true)

	obj2 = []
	obj2.foo(false)

	obj3 = []
	obj3.foo(true)
	```

	This is because vm_setivar_default calls rb_ensure_generic_iv_list_size
	to resize the iv list. However, the call to gen_ivtbl_resize reallocs
	the iv list, and then inserts into the generic iv table. If the
	st_insert triggers a GC then the old iv list will be read during
	marking, causing a use-after-free bug.

	Co-Authored-By: Jemma Issroff <jemmaissroff@gmail.com>
	---
	 internal/variable.h |  2 +-
	 variable.c          | 23 ++++++++++++++++++-----
	 vm_insnhelper.c     |  4 ++--
	 3 files changed, 21 insertions(+), 8 deletions(-)
---
 variable.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

(limited to 'variable.c')

diff --git a/variable.c b/variable.c
index 0fd4a80887..c409209117 100644
--- a/variable.c
+++ b/variable.c
@@ -66,7 +66,10 @@ static st_table *generic_iv_tbl_;
 struct ivar_update {
     struct gen_ivtbl *ivtbl;
     uint32_t iv_index;
-    rb_shape_t* shape;
+    uint32_t max_index;
+#if !SHAPE_IN_BASIC_FLAGS
+    rb_shape_t *shape;
+#endif
 };
 
 void
@@ -1018,7 +1021,7 @@ generic_ivar_update(st_data_t *k, st_data_t *v, st_data_t u, int existing)
         }
     }
     FL_SET((VALUE)*k, FL_EXIVAR);
-    ivtbl = gen_ivtbl_resize(ivtbl, ivup->shape->next_iv_index);
+    ivtbl = gen_ivtbl_resize(ivtbl, ivup->max_index);
     // Reinsert in to the hash table because ivtbl might be a newly resized chunk of memory
     *v = (st_data_t)ivtbl;
     ivup->ivtbl = ivtbl;
@@ -1281,7 +1284,10 @@ generic_ivar_set(VALUE obj, ID id, VALUE val)
         RUBY_ASSERT(index == (shape->next_iv_index - 1));
     }
 
+    ivup.max_index = shape->next_iv_index;
+#if !SHAPE_IN_BASIC_FLAGS
     ivup.shape = shape;
+#endif
 
     RB_VM_LOCK_ENTER();
     {
@@ -1382,15 +1388,22 @@ rb_ensure_iv_list_size(VALUE obj, uint32_t current_capacity, uint32_t new_capaci
 }
 
 struct gen_ivtbl *
-rb_ensure_generic_iv_list_size(VALUE obj, uint32_t newsize)
+rb_ensure_generic_iv_list_size(VALUE obj, rb_shape_t *shape, uint32_t newsize)
 {
     struct gen_ivtbl * ivtbl = 0;
 
     RB_VM_LOCK_ENTER();
     {
         if (UNLIKELY(!gen_ivtbl_get_unlocked(obj, 0, &ivtbl) || newsize > ivtbl->numiv)) {
-            ivtbl = gen_ivtbl_resize(ivtbl, newsize);
-            st_insert(generic_ivtbl_no_ractor_check(obj), (st_data_t)obj, (st_data_t)ivtbl);
+            struct ivar_update ivup = {
+                .iv_index = newsize - 1,
+                .max_index = newsize,
+#if !SHAPE_IN_BASIC_FLAGS
+                .shape = shape
+#endif
+            };
+            st_update(generic_ivtbl_no_ractor_check(obj), (st_data_t)obj, generic_ivar_update, (st_data_t)&ivup);
+            ivtbl = ivup.ivtbl;
             FL_SET_RAW(obj, FL_EXIVAR);
         }
     }
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