From 8bec2c788f3432f24788a2e7487486e20543e063 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Sat, 8 Aug 2009 13:49:00 -0700
Subject: [PATCH] nasm.c: fix stack overrun in assemble_file

If [DEBUG id] has id longer then 80 symbols (well, 79 actually plus
EOS) then stack will be just overwritten.

Fix it with explicit check for identifier being too long.

Based on an initial version by Cyrill Gorcunov <gorcunov@gmail.com>.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
---
 nasm.c | 46 +++++++++++++++++++++++++++++++---------------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/nasm.c b/nasm.c
index 8d728355..7bf7c570 100644
--- a/nasm.c
+++ b/nasm.c
@@ -1162,7 +1162,7 @@ static enum directives getkw(char **directive, char **value);
 
 static void assemble_file(char *fname, StrList **depend_ptr)
 {
-    char *directive, *value, *p, *q, *special, *line, debugid[80];
+    char *directive, *value, *p, *q, *special, *line;
     insn output_ins;
     int i, validid;
     bool rn_error;
@@ -1395,27 +1395,43 @@ static void assemble_file(char *fname, StrList **depend_ptr)
                     location.segment = NO_SEG;
                     break;
                 case D_DEBUG:		/* [DEBUG] */
+		{
+		    char debugid[128];
+		    bool badid, overlong;
+
                     p = value;
                     q = debugid;
-                    validid = true;
-                    if (!isidstart(*p))
-                        validid = false;
-                    while (*p && !nasm_isspace(*p)) {
-                        if (!isidchar(*p))
-                            validid = false;
-                        *q++ = *p++;
-                    }
-                    *q++ = 0;
-                    if (!validid) {
-                        nasm_error(passn == 1 ? ERR_NONFATAL : ERR_PANIC,
-                                     "identifier expected after DEBUG");
-                        break;
-                    }
+		    badid = overlong = false;
+                    if (!isidstart(*p)) {
+                        badid = true;
+		    } else {
+			while (*p && !nasm_isspace(*p)) {
+			    if (q >= debugid + sizeof debugid - 1) {
+				overlong = true;
+				break;
+			    }
+			    if (!isidchar(*p))
+				badid = true;
+			    *q++ = *p++;
+			}
+			*q = 0;
+		    }
+                    if (badid) {
+			nasm_error(passn == 1 ? ERR_NONFATAL : ERR_PANIC,
+				   "identifier expected after DEBUG");
+			break;
+		    }
+		    if (overlong) {
+			nasm_error(passn == 1 ? ERR_NONFATAL : ERR_PANIC,
+				   "DEBUG identifier too long");
+			break;
+		    }
                     while (*p && nasm_isspace(*p))
                         p++;
                     if (pass0 == 2)
                         dfmt->debug_directive(debugid, p);
                     break;
+		}
                 case D_WARNING:		/* [WARNING {+|-|*}warn-name] */
 		    while (*value && nasm_isspace(*value))
 			value++;
-- 
2.11.4.GIT