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[Bug 1535150] Re: overlayfs over fuse should refuse copy_up of files if uid/gid not mapped

To: kernel-packages@xxxxxxxxxxxxxxxxxxx
From: Launchpad Bug Tracker <1535150@xxxxxxxxxxxxxxxxxx>
Date: Wed, 24 Feb 2016 13:04:36 -0000
Reply-to: Bug 1535150 <1535150@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx
** Branch linked: lp:~ubuntu-branches/ubuntu/trusty/linux-lts-wily
/trusty-security

** Branch linked: lp:~ubuntu-branches/ubuntu/trusty/linux-lts-wily
/trusty-proposed

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https://bugs.launchpad.net/bugs/1535150

Title:
  overlayfs over fuse should refuse copy_up of files if uid/gid not
  mapped

Status in linux package in Ubuntu:
  Confirmed
Status in linux-armadaxp package in Ubuntu:
  Invalid
Status in linux-flo package in Ubuntu:
  New
Status in linux-goldfish package in Ubuntu:
  New
Status in linux-lts-quantal package in Ubuntu:
  Invalid
Status in linux-lts-raring package in Ubuntu:
  Invalid
Status in linux-lts-saucy package in Ubuntu:
  Invalid
Status in linux-lts-trusty package in Ubuntu:
  Invalid
Status in linux-lts-utopic package in Ubuntu:
  Invalid
Status in linux-lts-vivid package in Ubuntu:
  Invalid
Status in linux-lts-wily package in Ubuntu:
  Invalid
Status in linux-lts-xenial package in Ubuntu:
  Invalid
Status in linux-mako package in Ubuntu:
  New
Status in linux-manta package in Ubuntu:
  New
Status in linux-raspi2 package in Ubuntu:
  New
Status in linux-ti-omap4 package in Ubuntu:
  Invalid
Status in linux source package in Precise:
  New
Status in linux-armadaxp source package in Precise:
  New
Status in linux-flo source package in Precise:
  Invalid
Status in linux-goldfish source package in Precise:
  Invalid
Status in linux-lts-quantal source package in Precise:
  Invalid
Status in linux-lts-raring source package in Precise:
  Invalid
Status in linux-lts-saucy source package in Precise:
  Invalid
Status in linux-lts-trusty source package in Precise:
  Fix Released
Status in linux-lts-utopic source package in Precise:
  Invalid
Status in linux-lts-vivid source package in Precise:
  Invalid
Status in linux-lts-wily source package in Precise:
  Invalid
Status in linux-lts-xenial source package in Precise:
  Invalid
Status in linux-mako source package in Precise:
  Invalid
Status in linux-manta source package in Precise:
  Invalid
Status in linux-raspi2 source package in Precise:
  Invalid
Status in linux-ti-omap4 source package in Precise:
  New
Status in linux source package in Trusty:
  Fix Released
Status in linux-armadaxp source package in Trusty:
  Invalid
Status in linux-flo source package in Trusty:
  Invalid
Status in linux-goldfish source package in Trusty:
  Invalid
Status in linux-lts-quantal source package in Trusty:
  Invalid
Status in linux-lts-raring source package in Trusty:
  Invalid
Status in linux-lts-saucy source package in Trusty:
  Invalid
Status in linux-lts-trusty source package in Trusty:
  Invalid
Status in linux-lts-utopic source package in Trusty:
  Fix Released
Status in linux-lts-vivid source package in Trusty:
  Fix Released
Status in linux-lts-wily source package in Trusty:
  Fix Released
Status in linux-lts-xenial source package in Trusty:
  New
Status in linux-mako source package in Trusty:
  Invalid
Status in linux-manta source package in Trusty:
  Invalid
Status in linux-raspi2 source package in Trusty:
  Invalid
Status in linux-ti-omap4 source package in Trusty:
  Invalid
Status in linux source package in Vivid:
  Fix Released
Status in linux-armadaxp source package in Vivid:
  New
Status in linux-flo source package in Vivid:
  New
Status in linux-goldfish source package in Vivid:
  New
Status in linux-lts-quantal source package in Vivid:
  New
Status in linux-lts-raring source package in Vivid:
  New
Status in linux-lts-saucy source package in Vivid:
  New
Status in linux-lts-trusty source package in Vivid:
  New
Status in linux-lts-utopic source package in Vivid:
  New
Status in linux-lts-vivid source package in Vivid:
  New
Status in linux-lts-wily source package in Vivid:
  New
Status in linux-lts-xenial source package in Vivid:
  New
Status in linux-mako source package in Vivid:
  New
Status in linux-manta source package in Vivid:
  New
Status in linux-raspi2 source package in Vivid:
  New
Status in linux-ti-omap4 source package in Vivid:
  New
Status in linux source package in Wily:
  Fix Released
Status in linux-armadaxp source package in Wily:
  Invalid
Status in linux-flo source package in Wily:
  New
Status in linux-goldfish source package in Wily:
  New
Status in linux-lts-quantal source package in Wily:
  Invalid
Status in linux-lts-raring source package in Wily:
  Invalid
Status in linux-lts-saucy source package in Wily:
  Invalid
Status in linux-lts-trusty source package in Wily:
  Invalid
Status in linux-lts-utopic source package in Wily:
  Invalid
Status in linux-lts-vivid source package in Wily:
  Invalid
Status in linux-lts-wily source package in Wily:
  Invalid
Status in linux-lts-xenial source package in Wily:
  Invalid
Status in linux-mako source package in Wily:
  New
Status in linux-manta source package in Wily:
  New
Status in linux-raspi2 source package in Wily:
  Fix Released
Status in linux-ti-omap4 source package in Wily:
  Invalid
Status in linux source package in Xenial:
  Confirmed
Status in linux-armadaxp source package in Xenial:
  Invalid
Status in linux-flo source package in Xenial:
  New
Status in linux-goldfish source package in Xenial:
  New
Status in linux-lts-quantal source package in Xenial:
  Invalid
Status in linux-lts-raring source package in Xenial:
  Invalid
Status in linux-lts-saucy source package in Xenial:
  Invalid
Status in linux-lts-trusty source package in Xenial:
  Invalid
Status in linux-lts-utopic source package in Xenial:
  Invalid
Status in linux-lts-vivid source package in Xenial:
  Invalid
Status in linux-lts-wily source package in Xenial:
  Invalid
Status in linux-lts-xenial source package in Xenial:
  Invalid
Status in linux-mako source package in Xenial:
  New
Status in linux-manta source package in Xenial:
  New
Status in linux-raspi2 source package in Xenial:
  New
Status in linux-ti-omap4 source package in Xenial:
  Invalid

Bug description:
  On Ubuntu Wily it is possible to place an USERNS overlayfs mount over
  a fuse mount. The fuse filesystem may contain SUID binaries, but those
  cannot be executed due to nosuid mount options. But when touching such
  an SUID binary via overlayfs mount, this will trigger copy_up
  including all file attributes, thus creating a real SUID binary on the
  disk.

  Sequence:
  * Mount fuse filesystem exposing one world writable SUID binary
  * Create USERNS
  * Mount overlayfs on top of fuse
  * open the SUID binary RDWR in overlayfs, thus triggering copy_up

  Afterwards the SUID binary can be invoked to gain root privileges.

  For additional information, test tool see
  http://www.halfdog.net/Security/2016/OverlayfsOverFusePrivilegeEscalation/
  (InvitedOnly/3YD9ufze) and attached sharing policy.

  
  $ lsb_release -rd
  Description:    Ubuntu 15.10
  Release:        15.10

  $ apt-cache policy linux-image-4.2.0-23-generic
  linux-image-4.2.0-23-generic:
    Installed: 4.2.0-23.28
    Candidate: 4.2.0-23.28
    Version table:
   *** 4.2.0-23.28 0
          500 http://archive.ubuntu.com/ubuntu/ wily-updates/main amd64 Packages
          500 http://archive.ubuntu.com/ubuntu/ wily-security/main amd64 Packages
          100 /var/lib/dpkg/status

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