From: cgf AT cygnus DOT com (Christopher Faylor)
Subject: Re: script execution bug
20 Nov 1998 11:36:57 -0800
Message-ID: <19981120142057.A20838.cygnus.cygwin32.developers@cygnus.com>
References: <uww4qtsxk DOT fsf AT parvati DOT will DOT or DOT jp>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
To: Kazuhiro Fujieda <fujieda AT jaist DOT ac DOT jp>, cygwin32-developers AT cygnus DOT com

On Fri, Nov 20, 1998 at 10:06:15PM +0900, Kazuhiro Fujieda wrote:
>I'm sorry for my poor English and poor patches every time,
>but...
>
>When a script file of which interpreter doesn't exist is
>executed in winsup-981116, a null pointer dereference occur at
>spawn.cc:288. It should be checked whether 'ext' is null
>after find_exec() is called at spawn.cc:358.
>
>In the first place, spawn_guts() doesn't need to call
>find_exec() because POSIX specified that the interpreter is
>executed by execve(). I believe spawn.cc:358 can be replaced as
>the following patch.

I agree that what cygwin is doing is not POSIX but we apparently
now have a number of people on the mailing list using this
"feature" so I don't believe that we can remove it without
generating a lot of confusion and dissatisfaction.

Does the patch below solve the problem?

-chris

Index: spawn.cc
===================================================================
RCS file: /cvs/cvsfiles/devo/winsup/spawn.cc,v
retrieving revision 1.90
diff -u -p -r1.90 spawn.cc
--- spawn.cc	1998/11/19 23:31:00	1.90
+++ spawn.cc	1998/11/20 19:20:33
@@ -47,15 +47,12 @@ perhaps_suffix (const char *prog, char *
 
   if (temp.file_attributes () & FILE_ATTRIBUTE_DIRECTORY)
     ext = NULL;
+  else if (temp.known_suffix)
+    ext = buf + (temp.known_suffix - temp.get_win32 ());
   else
-    {
-      if (temp.known_suffix)
-	ext = buf + (temp.known_suffix - temp.get_win32 ());
-      else
-	ext = strchr (temp.get_win32 (), '\0');
-    }
+    ext = strchr (buf, '\0');
 
-  debug_printf ("buf %s, suffix found '%s'", buf, ext ?: "(none)");
+  debug_printf ("buf %s, suffix found '%s'", buf, ext);
   return ext;
 }
 
@@ -63,7 +60,7 @@ perhaps_suffix (const char *prog, char *
    suffixes to it.  The win32-translated name is placed in 'buf'.
    Any found suffix is returned in known_suffix.
 
-   If the file is not found and !null_if_not_foudn then the win32 version
+   If the file is not found and !null_if_not_found then the win32 version
    of name is placed in buf and returned.  Otherwise the contents of buf
    is undefined and NULL is returned.  */
 
@@ -73,6 +70,7 @@ find_exec (const char *name, char *buf, 
 {
   const char *suffix = "";
   debug_printf ("find_exec (%s)", name);
+  char *retval = buf;
 
   /* Check to see if file can be opened as is first.
      Win32 systems always check . first, but PATH may not be set up to
@@ -119,15 +117,15 @@ errout:
   /* Couldn't find anything in the given path.
      Take the appropriate action based on null_if_not_found. */
   if (null_if_notfound)
-    buf = NULL;
+    retval = NULL;
   else
     strcpy (buf, path_conv (name).get_win32 ());
 
 out:
   debug_printf ("%s = find_exec (%s)", buf, name);
   if (known_suffix)
-    *known_suffix = suffix;
-  return buf;
+    *known_suffix = suffix ?: strchr (buf, '\0');
+  return retval;
 }
 
 /* Utility for spawn_guts.  */