[Nasm-devel] [PATCH v2] preproc: prohibit unmacro while macro expansion

[Igor Munkin]

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 at cpan.org>
---
 asm/preproc.c                |  13 ++++++++++++
 travis/test/br3392531.asm    | Bin 0 -> 366 bytes
 travis/test/br3392531.json   |  12 ++++++++++++
 travis/test/br3392531.stderr |  29 +++++++++++++++++++++++++++
 travis/test/br3392716.asm    | Bin 0 -> 237 bytes
 travis/test/br3392716.json   |  13 ++++++++++++
 travis/test/br3392716.stderr |  37 +++++++++++++++++++++++++++++++++++
 7 files changed, 104 insertions(+)
 create mode 100644 travis/test/br3392531.asm
 create mode 100644 travis/test/br3392531.json
 create mode 100644 travis/test/br3392531.stderr
 create mode 100644 travis/test/br3392716.asm
 create mode 100644 travis/test/br3392716.json
 create mode 100644 travis/test/br3392716.stderr

diff --git a/asm/preproc.c b/asm/preproc.c
index 69543174..ab229c9c 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -4330,6 +4330,19 @@ issue_error:
             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 &&
diff --git a/travis/test/br3392531.asm b/travis/test/br3392531.asm
new file mode 100644
index 0000000000000000000000000000000000000000..6ef2c6894fcac1bf1a384eb7e24fb513cd7f04df
GIT binary patch
literal 366
zcmZ9Iu}%U(6h$}M4V^88FL56+Ah;ufM1mL^jhdJcEft5|f!$(fHZyM<iJ`IDPq4D_
zWBdyff56UCXR%T1d(X|u9b8G96IhC*F)%glpxbTt+O27#80)h|hw}qA+=_{^!<wKZ
z!a>m83wkcYRD?!@l_4csd3+}X-mJ4TfL+XT8~f|Q&C at dg;Jut-qjFm31!5k>6X9Dj
z`ML6j0M~$Tnr`V4Hks?fT-s?37yD)7Sc!D>(Bbvw-L~Iq0wU>;2{v3t?`obdtHldH
zT45!Mx%#67Ak3VhR8h(bOnx${vQLy>Q7T at IW-Jpr1or{0R?xo~pEyddIVdwa++fQ}
mA1F?&msk)$t_d at 3{L#34s+5pbhQB1_KMBu?$?^`!F7-EpDR0F9

literal 0
HcmV?d00001

diff --git a/travis/test/br3392531.json b/travis/test/br3392531.json
new file mode 100644
index 00000000..1a4c7bf6
--- /dev/null
+++ b/travis/test/br3392531.json
@@ -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" }
+		]
+	}
+]
diff --git a/travis/test/br3392531.stderr b/travis/test/br3392531.stderr
new file mode 100644
index 00000000..84810b64
--- /dev/null
+++ b/travis/test/br3392531.stderr
@@ -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 at 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
diff --git a/travis/test/br3392716.asm b/travis/test/br3392716.asm
new file mode 100644
index 0000000000000000000000000000000000000000..ac480f3038e3437b598179532ee1655a8daef70c
GIT binary patch
literal 237
zcmb2neaEF*nwOiHT$Hbnh+roq=47Tfb15h&sDkA{^5|j;3dO}GT&hKK$p)%?1-dE@
z$uf}v$??g$1_sG&@7}$8`w3w*L}_YXO0^x(BrdLE6wL-CYA!BOP&Y(4PC<d8n3+oz
SXnHQxbc6!c<dA%*UG4xY`b-!A

literal 0
HcmV?d00001

diff --git a/travis/test/br3392716.json b/travis/test/br3392716.json
new file mode 100644
index 00000000..b3d4e0b1
--- /dev/null
+++ b/travis/test/br3392716.json
@@ -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" }
+		]
+	}
+]
diff --git a/travis/test/br3392716.stderr b/travis/test/br3392716.stderr
new file mode 100644
index 00000000..049bcb94
--- /dev/null
+++ b/travis/test/br3392716.stderr
@@ -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
-- 
2.29.2