patch 9.0.2129: [security]: use-after-free in call_dfunc() Commit: https://github.com/vim/vim/commit/a555069b7d790abedc60edc505bd35bda257949d Author: mityu <mityu.mail@gmail.com> Date: Sat Nov 25 15:41:20 2023 +0100 patch 9.0.2129: [security]: use-after-free in call_dfunc() Problem: [security]: use-after-free in call_dfunc() Solution: Refresh dfunc pointer closes: #13571 This Commit fixes a SEGV caused by a use-after-free bug in call_dfunc(). When calling check_ufunc_arg_types() from the call_dfunc() it may cause def functions to be re-compiled and if there are too many def functions, the def_functions array will be re-allocated. Which means, that the dfunc pointer in call_dfunc() now starts pointing to freed memory. So we need to reset the dfunc pointer after calling check_ufunc_arg_types(). Let's also add a test, to ensure we do not regress. Signed-off-by: mityu <mityu.mail@gmail.com> Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com> Signed-off-by: Christian Brabandt <cb@256bit.org>

--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -548,6 +548,12 @@ call_dfunc(
     if (check_ufunc_arg_types(ufunc, argcount, vararg_count, ectx) == FAIL)
 	return FAIL;
 
+    // While check_ufunc_arg_types call, def function compilation process may
+    // run.  If so many def functions are compiled, def_functions array may be
+    // reallocated and dfunc may no longer have valid pointer.  Get the object
+    // pointer from def_functions again here.
+    dfunc = ((dfunc_T *)def_functions.ga_data) + cdf_idx;
+
     // Reserve space for:
     // - missing arguments
     // - stack frame