[Parted-maintainers] _primary_constraint(): start_geom is uninitialized if min_geom==0 && cylinder_size < dev->length. Debian bug #602568

[Jean-Christian de Rivaz]

Jean-Christian de Rivaz a écrit :
> The first 5MB device have, acoording to parted-2.3, a cylinder size 
> (16065) not smaller than the device length (10240), causing the 
> PedGeometry start_geom of the function _primary_constraint() (file 
> libparted/labels/dos.c) to stay uninitialized. I suspect that the 
> condition "cylinder_size < dev->length" have bee introduced for the 
> memory-mapped test as explained into the comment above the condition. 
> Unfortunately, it seem that the true real world contain at least a type 
> of USB key sold with a storage device that go wrong with this condition.

It seem that the only maintained source archive for GNU parted is
git://git.debian.org/git/parted/parted.git . Right ?

I found the this bug was introduced by this commit:

commit c79d91ec71882a1673daae0482aa90c514c63cc1
Author: Jim Meyering <meyering at redhat.com>
Date:   Tue Mar 30 16:50:59 2010 +0200

     dos: accommodate very small devices (useful for testing)

     * libparted/labels/dos.c (_primary_constraint): Don't pass a negative
     "device_length" to ped_geometry_init when the underlying device
     has fewer sectors than a "cylinder".

diff --git a/libparted/labels/dos.c b/libparted/labels/dos.c
index 752f186..8679c49 100644
--- a/libparted/labels/dos.c
+++ b/libparted/labels/dos.c
@@ -1616,8 +1616,13 @@ _primary_constraint (const PedDisk* disk, const
PedCHSGeometry* bios_geom,
                                         dev->length - min_geom->end))
                         return NULL;
         } else {
-               if (!ped_geometry_init (&start_geom, dev, cylinder_size,
-                                       dev->length - cylinder_size))
+               /* Do not assume that length is larger than 1 cylinder's
+                  worth of sectors.  This is useful when testing with
+                  a memory-mapped "disk" (a la scsi_debug) that is say,
+                  2048 sectors long.  */
+               if (cylinder_size < dev->length
+                   && !ped_geometry_init (&start_geom, dev, cylinder_size,
+                                          dev->length - cylinder_size))
                         return NULL;
                 if (!ped_geometry_init (&end_geom, dev, 0, dev->length))
                         return NULL;

Jean-Christian de Rivaz