If you deleted the fake partition on a loop label, loop_write() would write
the loop signature to the device, zeroing out all other bytes in the first
sector. When the disk contained an ext[234] filesystem and was using 2k
sectors, this would trash the super block residing in the 1-2kb part of the
sector causing the disk to become unrecognized. Instead, read the existing
sector and only modify the first few bytes that contain the loop label.
---
libparted/labels/loop.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/libparted/labels/loop.c b/libparted/labels/loop.c
index 8ebb1f4..98f9f23 100644
--- a/libparted/labels/loop.c
+++ b/libparted/labels/loop.c
@@ -170,7 +170,8 @@ loop_write (const PedDisk* disk)
/* if there is already a filesystem on the disk, we don't need to write
the signature */
if (part && part->fs_type)
return 1;
- memset (buf, 0, buflen);
+ if (!ped_device_read (disk->dev, buf, 0, 1))
+ return 0;
strcpy (buf, LOOP_SIGNATURE);
return ped_device_write (disk->dev, buf, 0, 1);
--
1.9.1
