patch 9.0.2149: [security]: use-after-free in exec_instructions() Commit: https://github.com/vim/vim/commit/5dd41d4b6370b7b7d09d691f9252b3899c66102a Author: Christian Brabandt <cb@256bit.org> Date: Mon Dec 4 22:52:23 2023 +0100 patch 9.0.2149: [security]: use-after-free in exec_instructions() Problem: [security]: use-after-free in exec_instructions() Solution: get tv pointer again [security]: use-after-free in exec_instructions() exec_instructions may access freed memory, if the GA_GROWS_FAILS() re-allocates memory. When this happens, the typval tv may still point to now already freed memory. So let's get that pointer again and compare it with tv. If those two pointers differ, tv is now invalid and we have to refresh the tv pointer. closes: #13621 Signed-off-by: Christian Brabandt <cb@256bit.org>

--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -4123,8 +4123,22 @@ exec_instructions(ectx_T *ectx)
 				      + iptr->isn_arg.outer.outer_idx;
 		    if (iptr->isn_type == ISN_LOADOUTER)
 		    {
+			typval_T *copy;
 			if (GA_GROW_FAILS(&ectx->ec_stack, 1))
 			    goto theend;
+			// careful: ga_grow_inner may re-alloc the stack
+			if (depth < 0)
+			    copy = ((typval_T *)outer->out_loop[-depth - 1]
+								   .stack->ga_data)
+					      + outer->out_loop[-depth - 1].var_idx
+					      + iptr->isn_arg.outer.outer_idx;
+			else
+			    copy = ((typval_T *)outer->out_stack->ga_data)
+					  + outer->out_frame_idx + STACK_FRAME_SIZE
+					  + iptr->isn_arg.outer.outer_idx;
+			// memory was freed, get tv again
+			if (copy != tv)
+			    tv = copy;
 			copy_tv(tv, STACK_TV_BOT(0));
 			++ectx->ec_stack.ga_len;
 		    }