arc4random rather than zero padding in geom_eli

[Arjan van der Velde]

Hi!

Surprised by seeing streaks of zeros every 4k on my geli encrypted drive, I realized they are zero-padded sectors (i.e. the 9th sector underlying every encrypted 4K). I was wondering if it’d be a good idea to do this instead:

[freebsd .../geom/eli]$ svn diff
Index: g_eli_integrity.c
===================================================================
--- g_eli_integrity.c	(revision 343023)
+++ g_eli_integrity.c	(working copy)
@@ -472,7 +472,7 @@
 			 * only partially filled.
 			 */
 			if (bp->bio_cmd == BIO_WRITE)
-				memset(data + sc->sc_alen + data_secsize, 0,
+				arc4random_buf(data + sc->sc_alen + data_secsize,
 				    encr_secsize - sc->sc_alen - data_secsize);
 		}

[freebsd .../geom/eli]$

Thanks!

— Arjan