grub-probe can't probe large logical volumes (LVM)

Hi,

I've had a problem when using the `grub-probe` binary to probe large LVM partitions (for example, a 1.5 TB partition).

This problem was discovered/tested in an Ubuntu 12.04.5.

When trying to probe these large LVM partitions, we get erros like:

    $ grub-probe -vvv /PATH/TO/MY/LVM
    [...]
    grub-core/kern/disk.c:494: Read out of range: sector 0x0 (out of disk).
    [...]
    grub-probe: error: unknown filesystem.

This bug seems like this one: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1027363

So, a debug the problem and I discovered that the problem occurs due to an inappropriate multiplication in the file grub-core/disk/lvm.c:

    lv->size += seg->extent_count * vg->extent_size;

The lv->size var is an unsigned 64-bits integer. However, the next two vars are respectively an unsigned int and an int. As the result of (unsigned int) * (int) is an integer, it's very easy to get a multiplication overflow (in my case, the result of the multiplication was zero -> lv->size = 0, resulting in the "out of disk" error).

So, I'm proposing a patch for this bug (file lvm_big_size.patch, to be applied after all Debian patched):

    Index: grub2-1.99/grub-core/disk/lvm.c
    ===================================================================
    --- grub2-1.99.orig/grub-core/disk/lvm.c 2011-04-18 21:16:16.000000000 +0000
    +++ grub2-1.99/grub-core/disk/lvm.c 2015-07-16 03:05:41.624035502 +0000
     -629,7 +629,8 @@
           goto lvs_segment_fail;
         p += sizeof("type = \"") - 1;

    - lv->size += seg->extent_count * vg->extent_size;
    + lv->size += ((grub_uint64_t) seg->extent_count
    + * (grub_uint64_t) vg->extent_size);

         if (grub_memcmp (p, "striped\"",
            sizeof ("striped\"") - 1) == 0)

I have already tested this patch using the following commands and it worked:

    quilt push -a
    DEB_BUILD_OPTIONS=nocheck fakeroot debian/rules build/grub-coreboot

I'm attaching this patch.