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[Tim Gardner <tim.gardner@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Xenial)
   Importance: High
       Status: Confirmed

** Changed in: linux (Ubuntu Xenial)
       Status: Confirmed => In Progress

** Changed in: linux (Ubuntu Xenial)
     Assignee: (unassigned) => Tim Gardner (timg-tpi)

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https://bugs.launchpad.net/bugs/1555338

Title:
  Linux netfilter IPT_SO_SET_REPLACE memory corruption

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Xenial:
  In Progress

Bug description:
  [From https://code.google.com/p/google-security-
  research/issues/detail?id=758 ]

  A memory corruption vulnerability exists in the IPT_SO_SET_REPLACE
  ioctl in the netfilter code for iptables support. This ioctl is can be
  triggered by an unprivileged user on PF_INET sockets when unprivileged
  user namespaces are available (CONFIG_USER_NS=y). Android does not
  enable this option, but desktop/server distributions and Chrome OS
  will commonly enable this to allow for containers support or
  sandboxing.

  In the mark_source_chains function (net/ipv4/netfilter/ip_tables.c) it
  is possible for a user-supplied ipt_entry structure to have a large
  next_offset field. This field is not bounds checked prior to writing a
  counter value at the supplied offset:

  newpos = pos + e->next_offset;
  ...
  e = (struct ipt_entry *) (entry0 + newpos);
  e->counters.pcnt = pos;

  This means that an out of bounds 32-bit write can occur in a 64kb
  range from the allocated heap entry, with a controlled offset and a
  partially controlled write value ("pos") or zero. The attached proof-
  of-concept (netfilter_setsockopt_v3.c) triggers the corruption
  multiple times to set adjacent heap structures to zero.

  This issue affects (at least) kernel versions 3.10, 3.18 and 4.4. It
  appears that a similar codepath is accessible via
  arp_tables.c/ARPT_SO_SET_REPLACE as well.

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