From bdb7d194d07e1f8465870f1d0a388200d90ae8f3 Mon Sep 17 00:00:00 2001
From: Craig Rodrigues <rodrigc@FreeBSD.org>
Date: Sat, 10 Sep 2005 21:30:49 +0000
Subject: [PATCH] In ext2_mountfs(), check that the superblock size, SBSIZE, is
 aligned with the sectorsize value returned by GEOM, before doing a bread() of
 the superblock. This eliminates a panic when trying the following on an empty
 CD-ROM drive: mount_ext2fs /dev/acd0 /mnt

Reviewed by:	phk
---
 sys/gnu/fs/ext2fs/ext2_vfsops.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sys/gnu/fs/ext2fs/ext2_vfsops.c b/sys/gnu/fs/ext2fs/ext2_vfsops.c
index b801b974c759..84d1809b1419 100644
--- a/sys/gnu/fs/ext2fs/ext2_vfsops.c
+++ b/sys/gnu/fs/ext2fs/ext2_vfsops.c
@@ -612,6 +612,18 @@ ext2_mountfs(devvp, mp, td)
 	VOP_UNLOCK(devvp, 0, td);
 	if (error)
 		return (error);
+
+	/* XXX: should we check for some sectorsize or 512 instead? */
+	if (((SBSIZE % cp->provider->sectorsize) != 0) ||
+	    (SBSIZE < cp->provider->sectorsize)) {
+		DROP_GIANT();
+		g_topology_lock();
+		g_vfs_close(cp, td);
+		g_topology_unlock();
+		PICKUP_GIANT();
+		return (EINVAL);
+	}
+
 	bo = &devvp->v_bufobj;
 	bo->bo_private = cp;
 	bo->bo_ops = g_vfs_bufops;