fs/proc/base.c in the Linux kernel before 2.6.39.4 does not properly restrict access to /proc/#####/io files, which allows local users to obtain sensitive I/O statistics by polling a file, as demonstrated by discovering the length of another user’s password.
ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39.4
git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=1d1221f375c94ef961ba8574ac4f85c8870ddd51
rhn.redhat.com/errata/RHSA-2011-1212.html
www.openwall.com/lists/oss-security/2011/06/27/1
bugzilla.redhat.com/show_bug.cgi?id=716825
github.com/torvalds/linux/commit/1d1221f375c94ef961ba8574ac4f85c8870ddd51