CVE-2018-16872 Qemu: usb-mtp: path traversal by host filesystem manipulation in Media Transfer Protocol (MTP)

[P J P <ppandit () redhat com>]

  Hello,

A flaw was found in qemu Media Transfer Protocol (MTP). The code opening files 
in usb_mtp_get_object and usb_mtp_get_partial_object and directories in 
usb_mtp_object_readdir doesn't consider that the underlying filesystem may 
have changed since the time lstat(2) was called in usb_mtp_object_alloc, a 
classical TOCTTOU problem. An attacker with write access to the host 
filesystem shared with a guest can use this property to navigate the host 
filesystem in the context of the QEMU process and read any file the QEMU 
process has access to. Access to the filesystem may be local or via a network 
share protocol such as CIFS.

Upstream patch:
---------------
  -> https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg03135.html

This issue was reported by Michael Hanselmann.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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