8310265: (process) jspawnhelper should not use argv[0]

Reviewed-by: rriggs
Backport-of: 47d00a4cbeff5d757dda9c660dfd2385c02a57d7

Author: tstuefe

src/java.base/unix/native/jspawnhelper/jspawnhelper.c

@@ -136,14 +136,14 @@ void initChildStuff (int fdin, int fdout, ChildStuff *c) {
 int main(int argc, char *argv[]) {
     ChildStuff c;
     struct stat buf;
-    /* argv[0] contains the fd number to read all the child info */
+    /* argv[1] contains the fd number to read all the child info */
     int r, fdinr, fdinw, fdout;
     sigset_t unblock_signals;
 
 #ifdef DEBUG
     jtregSimulateCrash(0, 4);
 #endif
-    r = sscanf (argv[argc-1], "%d:%d:%d", &fdinr, &fdinw, &fdout);
+    r = sscanf (argv[1], "%d:%d:%d", &fdinr, &fdinw, &fdout);
     if (r == 3 && fcntl(fdinr, F_GETFD) != -1 && fcntl(fdinw, F_GETFD) != -1) {
         fstat(fdinr, &buf);
         if (!S_ISFIFO(buf.st_mode))

src/java.base/unix/native/libjava/ProcessImpl_md.c

@@ -488,16 +488,20 @@ spawnChild(JNIEnv *env, jobject process, ChildStuff *c, const char *helperpath)
     pid_t resultPid;
     int i, offset, rval, bufsize, magic;
     char *buf, buf1[(3 * 11) + 3]; // "%d:%d:%d\0"
-    char *hlpargs[2];
+    char *hlpargs[3];
     SpawnInfo sp;
 
     /* need to tell helper which fd is for receiving the childstuff
      * and which fd to send response back on
      */
     snprintf(buf1, sizeof(buf1), "%d:%d:%d", c->childenv[0], c->childenv[1], c->fail[1]);
-    /* put the fd string as argument to the helper cmd */
-    hlpargs[0] = buf1;
-    hlpargs[1] = 0;
+    /* NULL-terminated argv array.
+     * argv[0] contains path to jspawnhelper, to follow conventions.
+     * argv[1] contains the fd string as argument to jspawnhelper
+     */
+    hlpargs[0] = (char*)helperpath;
+    hlpargs[1] = buf1;
+    hlpargs[2] = NULL;
 
     /* Following items are sent down the pipe to the helper
      * after it is spawned.