git: 9front

Download patch

ref: b6110a0000e5c32b531056741347b1f8762c996a
parent: 8b36084e2b8283e6e895266e5a9b56a32c9133df
author: Ori Bernstein <ori@eigenstate.org>
date: Sun Apr 19 05:02:21 EDT 2020 

dont overflow the stack

when pushing expressions in cpp, particularly complex ones could
overflow the stack and silently corrupt our data structures. add
checks when we push, and bump the stack size up.


--- a/sys/src/cmd/cpp/eval.c
+++ b/sys/src/cmd/cpp/eval.c
@@ -2,7 +2,7 @@
 #include <libc.h>
 #include "cpp.h"
 
-#define	NSTAK	32
+#define	NSTAK	128
 #define	SGN	0
 #define	UNS	1
 #define	UND	2
@@ -136,6 +136,8 @@
 		case STRING:
 			if (rand)
 				goto syntax;
+			if(vp == vals + NSTAK)
+				goto fullstakdeveloper;
 			*vp++ = tokval(tp);
 			rand = 1;
 			continue;
@@ -146,6 +148,8 @@
 		case NOT:
 			if (rand)
 				goto syntax;
+			if(op == ops + NSTAK)
+				goto fullstakdeveloper;
 			*op++ = tp->type;
 			continue;
 
@@ -152,6 +156,8 @@
 		/* unary-binary */
 		case PLUS: case MINUS: case STAR: case AND:
 			if (rand==0) {
+				if(op == ops + NSTAK)
+					goto fullstakdeveloper;
 				if (tp->type==MINUS)
 					*op++ = UMINUS;
 				if (tp->type==STAR || tp->type==AND) {
@@ -171,6 +177,8 @@
 				goto syntax;
 			if (evalop(priority[tp->type])!=0)
 				return 0;
+			if(op == ops + NSTAK)
+				goto fullstakdeveloper;
 			*op++ = tp->type;
 			rand = 0;
 			continue;
@@ -178,6 +186,8 @@
 		case LP:
 			if (rand)
 				goto syntax;
+			if(op == ops + NSTAK)
+				goto fullstakdeveloper;
 			*op++ = LP;
 			continue;
 
@@ -211,6 +221,9 @@
 syntax:
 	error(ERROR, "Syntax error in #if/#elif");
 	return 0;
+fullstakdeveloper:
+	error(ERROR, "Out of stack space evaluating #if");
+	return 0;
 }
 
 int
@@ -375,6 +388,10 @@
 		}
 		v1.val = rv1;
 		v1.type = rtype;
+		if(op == ops + NSTAK){
+			error(ERROR, "Out of stack space evaluating #if");
+			return 0;
+		}
 		*vp++ = v1;
 	}
 	return 0;
-- 
⑨