preproc: prohibit unmacro while macro expansion

If macro is undefined while it's being expanded, use after free occurs,
since the MMacro instance is released, but it is still used to proceed
the expansion.

This change forbids macro undefinition: non-fatal error is raised and
the MMacro instance is not released if it is being processed by NASM
preprocessor.

Consider the following example:
| $ cat test.asm
| %macro m 0
| %unmacro m 0
| %endmacro
| m
| $ ./nasm test.asm
| test.asm:4: error: `%unmacro' can't undefine the macro being expanded
| test.asm:2: ... from macro `m' defined here

Fixes BR3392531 and BR3392716.

Signed-off-by: Igor Munkin <imun@cpan.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

Author: igormunkin

asm/preproc.c

@@ -4225,6 +4225,19 @@ static int do_directive(Token *tline, Token **output)
             goto done;
         }
         mmac_p = (MMacro **) hash_findi(&mmacros, spec.name, NULL);
+
+        /* Check the macro to be undefined is not being expanded */
+        list_for_each(l, istk->expansion) {
+            if (l->finishes == *mmac_p) {
+                nasm_nonfatal("`%%unmacro' can't undefine the macro being expanded");
+                /*
+                 * Do not release the macro instance to avoid using the freed
+                 * memory while proceeding the expansion.
+                 */
+                goto done;
+            }
+        }
+
         while (mmac_p && *mmac_p) {
             mmac = *mmac_p;
             if (mmac->casesense == spec.casesense &&

travis/test/br3392531.asm

@@ -0,0 +1,12 @@
+[
+	{
+		"description": "%unmacro is forbidden for macro being expanded",
+		"id": "br3392531",
+		"format": "bin",
+		"source": "br3392531.asm",
+		"error": "expected",
+		"target": [
+			{ "stderr": "br3392531.stderr" }
+		]
+	}
+]

travis/test/br3392531.json

@@ -0,0 +1,29 @@
+./travis/test/br3392531.asm:1: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:4: error: invalid decorator token inside braces
+./travis/test/br3392531.asm:4: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:5: error: parser: instruction expected
+./travis/test/br3392531.asm:7: error: `%macro' expects a parameter count
+./travis/test/br3392531.asm:11: warning: unterminated string [-w+other]
+./travis/test/br3392531.asm:14: error: parser: instruction expected
+./travis/test/br3392531.asm:17: error: `%$LRG': context stack is empty
+./travis/test/br3392531.asm:17: error: `%$LRG': context stack is empty
+./travis/test/br3392531.asm:17: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:18: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:19: error: parser: instruction expected
+./travis/test/br3392531.asm:20: error: `%1': not in a macro call
+./travis/test/br3392531.asm:20: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:21: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:8: ... from macro `section' defined here
+./travis/test/br3392531.asm:21: error: parser: instruction expected
+./travis/test/br3392531.asm:9: ... from macro `section' defined here
+./travis/test/br3392531.asm:21: error: label or instruction expected at start of line
+./travis/test/br3392531.asm:10: ... from macro `section' defined here
+./travis/test/br3392531.asm:21: error: invalid macro parameter: `%4stru@namB'
+./travis/test/br3392531.asm:11: ... from macro `section' defined here
+./travis/test/br3392531.asm:21: error: parser: instruction expected
+./travis/test/br3392531.asm:11: ... from macro `section' defined here
+./travis/test/br3392531.asm:21: error: `%unmacro' expects a parameter count
+./travis/test/br3392531.asm:12: ... from macro `section' defined here
+./travis/test/br3392531.asm:21: error: `%unmacro' can't undefine the macro being expanded
+./travis/test/br3392531.asm:12: ... from macro `section' defined here
+./travis/test/br3392531.asm:22: error: parser: instruction expected

travis/test/br3392531.stderr

@@ -0,0 +1,13 @@
+[
+	{
+		"description": "%unmacro is forbidden for macro being expanded",
+		"id": "br3392716",
+		"format": "macho64",
+		"source": "br3392716.asm",
+		"option": "-g",
+		"error": "expected",
+		"target": [
+			{ "stderr": "br3392716.stderr" }
+		]
+	}
+]

travis/test/br3392716.asm

@@ -0,0 +1,37 @@
+./travis/test/br3392716.asm:1: error: label or instruction expected at start of line
+./travis/test/br3392716.asm:2: error: `%unmacro' expects a parameter count
+./travis/test/br3392716.asm:3: warning: unterminated string [-w+other]
+./travis/test/br3392716.asm:3: error: `%unmacro' expects a macro name
+./travis/test/br3392716.asm:4: warning: unterminated string [-w+other]
+./travis/test/br3392716.asm:4: error: label or instruction expected at start of line
+./travis/test/br3392716.asm:5: error: `%macro' expects a parameter count
+./travis/test/br3392716.asm:15: warning: unterminated string [-w+other]
+./travis/test/br3392716.asm:20: warning: unterminated string [-w+other]
+./travis/test/br3392716.asm:20: warning: multi-line macro `sst' exists, but not taking 1 parameter [-w+macro-params-multi]
+./travis/test/br3392716.asm:20: error: parser: instruction expected
+./travis/test/br3392716.asm:21: error: `%%cTo': not in a macro call
+./travis/test/br3392716.asm:21: error: label or instruction expected at start of line
+./travis/test/br3392716.asm:6: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: `%unmacro' expects a parameter count
+./travis/test/br3392716.asm:7: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: `%unmacro' can't undefine the macro being expanded
+./travis/test/br3392716.asm:7: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: label or instruction expected at start of line
+./travis/test/br3392716.asm:8: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: parser: instruction expected
+./travis/test/br3392716.asm:10: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: label or instruction expected at start of line
+./travis/test/br3392716.asm:11: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: `%unmacro' expects a parameter count
+./travis/test/br3392716.asm:12: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: `%unmacro' can't undefine the macro being expanded
+./travis/test/br3392716.asm:12: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: label or instruction expected at start of line
+./travis/test/br3392716.asm:13: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: parser: instruction expected
+./travis/test/br3392716.asm:15: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: `%macro' expects a macro name
+./travis/test/br3392716.asm:16: ... from macro `sst' defined here
+./travis/test/br3392716.asm:21: error: parser: instruction expected
+./travis/test/br3392716.asm:17: ... from macro `sst' defined here
+./travis/test/br3392716.asm:22: error: label or instruction expected at start of line