[Bug 1475337] Re: grub-probe can't probe large logical volumes (LVM)

[Rarylson Freitas]

I've discovered that the seg->extent_count  and vg->extent_size counters
are 64 bits in the upstream.

So, the problem is only in the Ubuntu 12.04 LTS release (I don't know if
it exists in the Ubuntu 14.04 LTS.

So, consider applying this patch in Ubuntu 12.04 or backporting the
64bit counters to Ubuntu 12.04.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to grub2 in Ubuntu.
https://bugs.launchpad.net/bugs/1475337

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

Status in grub2 package in Ubuntu:
  New

Bug description:
  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.

  Additional info: I discovered that this bug already exists in the GRUB
  upstream (file grub-core/disk/lvm.c, line 466). I will also report
  after this bug for them.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1475337/+subscriptions