Return a more meaningful errno when the length of the interpreter

exceeds MAXSHELLCMDLEN to avoid secondary /bin/sh execution.

Update execve man page to reflect change.

Increase MAXSHELLCMDLEN to a slightly more meaningful value.

PR:		kern/32106
Submitted by:	b@etek.chalmers.se
Reviewed by:	bsd
MFC after:	2 weeks

lib/libc/sys/execve.2

@@ -210,6 +210,9 @@ A component of the path prefix is not a directory.
 .It Bq Er ENAMETOOLONG
 A component of a pathname exceeded 255 characters,
 or an entire path name exceeded 1023 characters.
+.It Bq Er ENAMETOOLONG
+When invoking an interpreted script, the interpreter name
+exceeds MAXSHELLCMDLEN characters.
 .It Bq Er ENOENT
 The new process file does not exist.
 .It Bq Er ELOOP

sys/kern/imgact_shell.c

@@ -74,7 +74,7 @@ exec_shell_imgact(imgp)
 	 */
 	for (ihp = &image_header[2]; *ihp != '\n' && *ihp != '#'; ++ihp) {
 		if (ihp >= &image_header[MAXSHELLCMDLEN])
-			return(ENOEXEC);
+			return(ENAMETOOLONG);
 	}
 	line_endp = ihp;
 

sys/sys/imgact.h

@@ -36,7 +36,7 @@
 #ifndef _SYS_IMGACT_H_
 #define	_SYS_IMGACT_H_
 
-#define MAXSHELLCMDLEN	64
+#define MAXSHELLCMDLEN	128
 
 struct image_params {
 	struct proc *proc;	/* our process struct */