Description of problem:
User "foo" can use the SWAPEXT ioctl to swap a write-only file owned by user "bar" into a file owned by "foo" and subsequently reading it. It does so by checking that the file descriptors passed to the ioctl are also opened for reading.
Red Hat would like to thank Dan Rosenberg for reporting this issue.
This issue did not affect the version of Linux kernel as shipped with Red Hat
Enterprise Linux 3, 4 and Red Hat Enterprise MRG as they did not include
support for the XFS filesystem. A future kernel update in Red Hat Enterprise
Linux 5 will address this issue.
This issue has been addressed in following products:
Red Hat Enterprise Linux 5
Via RHSA-2010:0610 https://rhn.redhat.com/errata/RHSA-2010-0610.html