[Bug 1469143] [NEW] kpartx -d fails with image paths longer than 63 characters

[Simo Punnonen]

Public bug reported:

$ apt-show-versions multipath-tools
multipath-tools:amd64/vivid 0.4.9-3ubuntu12 uptodate

Reproduce:
Mount an image from a path longer than 63 chars succeeds:
$ sudo kpartx -av asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12asdf13/disk.img
add map loop0p1 (252:0): 0 409600 linear /dev/loop0 2048
add map loop0p2 (252:1): 0 2 linear /dev/loop0 411648
add map loop0p5 : 0 819200 linear /dev/loop0 413696
add map loop0p6 : 0 819200 linear /dev/loop0 1234944
add map loop0p7 : 0 819200 linear /dev/loop0 2056192
add map loop0p8 : 0 1316864 linear /dev/loop0 2877440

but dismounting fails:
$ sudo kpartx -dv asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12asdf13/disk.img

strace shows that the parameter on the dismount appears to get cut at 63 chars:
ioctl(3, DM_LIST_VERSIONS, 0x15b89b0)   = 0
stat("asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12asdf13/disk.img", {st_mode=S_IFREG|0644, st_size=2147483648, ...}) = 0
stat("/dev/loop0", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 0), ...}) = 0
open("/dev/loop0", O_RDONLY)            = 4
ioctl(4, LOOP_GET_STATUS, {number=0, offset=0, flags=0, name="asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12a", ...}) = 0
close(4)                                = 0
stat("/dev/loop1", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 1), ...}) = 0
open("/dev/loop1", O_RDONLY)            = 4
ioctl(4, LOOP_GET_STATUS, {number=0, offset=0, flags=0, name="asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12a", ...}) = -1 ENXIO (No such device or address)

if the path is 63 chars or less, the dismount also succeeds.

This is quickly becomes an issue if you want to use full disk paths in
your shell scripts.

** Affects: multipath-tools (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: kpartx

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https://bugs.launchpad.net/bugs/1469143

Title:
  kpartx -d fails with image paths longer than 63 characters

Status in multipath-tools package in Ubuntu:
  New

Bug description:
  $ apt-show-versions multipath-tools
  multipath-tools:amd64/vivid 0.4.9-3ubuntu12 uptodate

  Reproduce:
  Mount an image from a path longer than 63 chars succeeds:
  $ sudo kpartx -av asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12asdf13/disk.img
  add map loop0p1 (252:0): 0 409600 linear /dev/loop0 2048
  add map loop0p2 (252:1): 0 2 linear /dev/loop0 411648
  add map loop0p5 : 0 819200 linear /dev/loop0 413696
  add map loop0p6 : 0 819200 linear /dev/loop0 1234944
  add map loop0p7 : 0 819200 linear /dev/loop0 2056192
  add map loop0p8 : 0 1316864 linear /dev/loop0 2877440

  but dismounting fails:
  $ sudo kpartx -dv asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12asdf13/disk.img

  strace shows that the parameter on the dismount appears to get cut at 63 chars:
  ioctl(3, DM_LIST_VERSIONS, 0x15b89b0)   = 0
  stat("asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12asdf13/disk.img", {st_mode=S_IFREG|0644, st_size=2147483648, ...}) = 0
  stat("/dev/loop0", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 0), ...}) = 0
  open("/dev/loop0", O_RDONLY)            = 4
  ioctl(4, LOOP_GET_STATUS, {number=0, offset=0, flags=0, name="asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12a", ...}) = 0
  close(4)                                = 0
  stat("/dev/loop1", {st_mode=S_IFBLK|0660, st_rdev=makedev(7, 1), ...}) = 0
  open("/dev/loop1", O_RDONLY)            = 4
  ioctl(4, LOOP_GET_STATUS, {number=0, offset=0, flags=0, name="asfd1asdf2asdf3asdf4asdf5asdf6asfd7asdf8asdf9asf10asdf11asdf12a", ...}) = -1 ENXIO (No such device or address)

  if the path is 63 chars or less, the dismount also succeeds.

  This is quickly becomes an issue if you want to use full disk paths in
  your shell scripts.

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