Bug#597563: grub-common: grub-probe segfaults scanning lvm devices

[Matthew Gabeler-Lee]

On 1/8/2011 18:55, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> I have a hypothesis. Does last partition on any device span, s.t. it
> leaves less than 64K after it until the end of device? If so then GRUB
> sees the same metadata sector as the one at the end of device and as at
> the end of partition. With 1.x metadata sector contains its own location
> on the device. With 0.90 I can see no such field. Is there a way to
> check for such condition with 0.90?
I created the last partition on each disk running as close to the end of the 
disk as fdisk would allow.  Since the partitions were created on cylinder 
boundaries, however, it looks like the last partition ends 2MB before the 
end of the physical device.  Reading the data between the end of the last 
partition and the end of the disk gives all zeros for three of the four 
disks, but /dev/sdb gives what looks like it might have an mdraid superblock 
in it:

$ sudo fdisk -lu /dev/sdb

Disk /dev/sdb: 750.2 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x994d834b

    Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *          63     4016249     2008093+  fd  Linux raid autodetect
/dev/sdb2         4016250     8032499     2008125   fd  Linux raid autodetect
/dev/sdb3         8032500  1465144064   728555782+  fd  Linux raid autodetect
$ sudo dd if=/dev/sdb bs=512 skip=1465144064 2>/dev/null | hd
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00260000  fc 4e 2b a9 00 00 00 00  5a 00 00 00 03 00 00 00  |.N+.....Z.......|
00260010  00 00 00 00 a2 f7 64 93  e8 36 28 44 01 00 00 00  |......d..6(D....|
00260020  80 f3 0e 00 03 00 00 00  02 00 00 00 00 00 00 00  |................|
00260030  00 00 00 00 d5 95 46 d7  a0 b3 8d 7d 48 9e 5f 3b  |......F....}H._;|
00260040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00260080  6f 90 65 49 01 00 00 00  02 00 00 00 03 00 00 00  |o.eI............|
00260090  00 00 00 00 01 00 00 00  eb 34 81 5b 52 25 90 00  |.........4.[R%..|
002600a0  00 00 00 00 52 25 90 00  00 00 00 00 ff ff ff ff  |....R%..........|
002600b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00260200  00 00 00 00 08 00 00 00  01 00 00 00 00 00 00 00  |................|
00260210  06 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00260220  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00260280  01 00 00 00 08 00 00 00  11 00 00 00 01 00 00 00  |................|
00260290  06 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
002602a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00260300  02 00 00 00 08 00 00 00  30 00 00 00 02 00 00 00  |........0.......|
00260310  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00260f80  02 00 00 00 08 00 00 00  30 00 00 00 02 00 00 00  |........0.......|
00260f90  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
0027e000

mdadm seems to confirm this.  mdadm --examine /dev/sd[acd] gives "no md 
superblock", but on /dev/sdb, I get this (note that the device size at least 
is bogus, since the disk itself is only 750GB):

$ sudo mdadm --examine /dev/sdb
/dev/sdb:
           Magic : a92b4efc
         Version : 0.90.03
            UUID : 9364f7a2:d74695d5:7d8db3a0:3b5f9e48
   Creation Time : Mon Mar 27 14:03:04 2006
      Raid Level : raid1
   Used Dev Size : 979840 (957.04 MiB 1003.36 MB)
      Array Size : 979840 (957.04 MiB 1003.36 MB)
    Raid Devices : 2
   Total Devices : 3
Preferred Minor : 0

     Update Time : Thu Jan  8 00:34:39 2009
           State : clean
  Active Devices : 2
Working Devices : 3
  Failed Devices : 0
   Spare Devices : 1
        Checksum : 5b8134eb - correct
          Events : 9446738


       Number   Major   Minor   RaidDevice State
this     2       8       48        2      spare   /dev/sdd

    0     0       8        1        0      active sync   /dev/sda1
    1     1       8       17        1      active sync   /dev/sdb1
    2     2       8       48        2      spare   /dev/sdd

-- 
	-Matt
"Reality is that which, when you stop believing in it, doesn't go away".
                 -- Philip K. Dick
GPG pubkey fingerprint: A57F B354 FD30 A502 795B 9637 3EF1 3F22 A85E 2AD1