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Date:      Sun, 22 May 2016 14:31:20 +0000 (UTC)
From:      Kevin Lo <kevlo@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r300423 - in head/sys: fs/ext2fs ufs/ffs
Message-ID:  <201605221431.u4MEVKXC007524@repo.freebsd.org>
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Author: kevlo
Date: Sun May 22 14:31:20 2016
New Revision: 300423
URL: https://svnweb.freebsd.org/changeset/base/300423

Log:
  arc4random() returns 0 to (2**32)−1, use an alternative to initialize
  i_gen if it's zero rather than a divide by 2.
  
  With inputs from  delphij, mckusick, rmacklem
  
  Reviewed by:	mckusick

Modified:
  head/sys/fs/ext2fs/ext2_alloc.c
  head/sys/fs/ext2fs/ext2_vfsops.c
  head/sys/ufs/ffs/ffs_alloc.c
  head/sys/ufs/ffs/ffs_vfsops.c

Modified: head/sys/fs/ext2fs/ext2_alloc.c
==============================================================================
--- head/sys/fs/ext2fs/ext2_alloc.c	Sun May 22 14:13:20 2016	(r300422)
+++ head/sys/fs/ext2fs/ext2_alloc.c	Sun May 22 14:31:20 2016	(r300423)
@@ -408,7 +408,8 @@ ext2_valloc(struct vnode *pvp, int mode,
 	/*
 	 * Set up a new generation number for this inode.
 	 */
-	ip->i_gen = arc4random();
+	while (ip->i_gen == 0 || ++ip->i_gen == 0)
+		ip->i_gen = arc4random();
 
 	vfs_timestamp(&ts);
 	ip->i_birthtime = ts.tv_sec;

Modified: head/sys/fs/ext2fs/ext2_vfsops.c
==============================================================================
--- head/sys/fs/ext2fs/ext2_vfsops.c	Sun May 22 14:13:20 2016	(r300422)
+++ head/sys/fs/ext2fs/ext2_vfsops.c	Sun May 22 14:31:20 2016	(r300423)
@@ -998,7 +998,8 @@ ext2_vget(struct mount *mp, ino_t ino, i
 	 * already have one. This should only happen on old filesystems.
 	 */
 	if (ip->i_gen == 0) {
-		ip->i_gen = random() + 1;
+		while (ip->i_gen == 0)
+			ip->i_gen = arc4random();
 		if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0)
 			ip->i_flag |= IN_MODIFIED;
 	}

Modified: head/sys/ufs/ffs/ffs_alloc.c
==============================================================================
--- head/sys/ufs/ffs/ffs_alloc.c	Sun May 22 14:13:20 2016	(r300422)
+++ head/sys/ufs/ffs/ffs_alloc.c	Sun May 22 14:31:20 2016	(r300423)
@@ -1102,8 +1102,8 @@ dup_alloc:
 	/*
 	 * Set up a new generation number for this inode.
 	 */
-	if (ip->i_gen == 0 || ++ip->i_gen == 0)
-		ip->i_gen = arc4random() / 2 + 1;
+	while (ip->i_gen == 0 || ++ip->i_gen == 0)
+		ip->i_gen = arc4random();
 	DIP_SET(ip, i_gen, ip->i_gen);
 	if (fs->fs_magic == FS_UFS2_MAGIC) {
 		vfs_timestamp(&ts);
@@ -2080,7 +2080,8 @@ gotit:
 		bzero(ibp->b_data, (int)fs->fs_bsize);
 		dp2 = (struct ufs2_dinode *)(ibp->b_data);
 		for (i = 0; i < INOPB(fs); i++) {
-			dp2->di_gen = arc4random() / 2 + 1;
+			while (dp2->di_gen == 0)
+				dp2->di_gen = arc4random();
 			dp2++;
 		}
 		/*

Modified: head/sys/ufs/ffs/ffs_vfsops.c
==============================================================================
--- head/sys/ufs/ffs/ffs_vfsops.c	Sun May 22 14:13:20 2016	(r300422)
+++ head/sys/ufs/ffs/ffs_vfsops.c	Sun May 22 14:31:20 2016	(r300423)
@@ -1768,7 +1768,8 @@ ffs_vgetf(mp, ino, flags, vpp, ffs_flags
 	 * already have one. This should only happen on old filesystems.
 	 */
 	if (ip->i_gen == 0) {
-		ip->i_gen = arc4random() / 2 + 1;
+		while (ip->i_gen == 0)
+			ip->i_gen = arc4random();
 		if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
 			ip->i_flag |= IN_MODIFIED;
 			DIP_SET(ip, i_gen, ip->i_gen);

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