[Bug 726283] Re: umount segfaults with inconsistent entry in /etc/fstab

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: util-linux (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/726283

Title:
  umount segfaults with inconsistent entry in /etc/fstab

Status in “util-linux” package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: util-linux

  Reproduced on Maverick using util-linux version 2.17.2-0ubuntu1.

  If /etc/fstab has an incorrect mount directory for an already mounted
  device, 'umount <device>' will segfault when run as an unprivileged
  user.

  Steps to reproduce:
  cd /tmp
  # Create and mount a loopback file
  dd if=/dev/zero of=file bs=1024 count=300; mkdir fs
  sudo losetup /dev/loop0 file; sudo mkfs /dev/loop0
  sudo mount /dev/loop0 fs/
  # Add entry to /etc/fstab with incorrect/missing mount directory
  echo /tmp/fs | sudo tee -a /etc/fstab
  # Try umounting as an unprivileged user
  umount /tmp/fs
  # Segfault!

  Applying the attached patch fixes the segfault.  The semantics of this
  patch are likely wrong, but at least this demonstrates the codepath
  taken (fs escapes from the revelant block being NULL, only to be
  dereferenced on the next line).

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