tree 3be06d07b410d4503609cc8e2a83c40cc7d093ee
parent b3623962bb6bb253d1504dd890bf87ac27556044
author Ben Hutchings <ben@decadent.org.uk> 1434489066 +0100
committer Patrick Tjin <pattjin@google.com> 1458244891 -0700

pipe: iovec: Fix memory corruption when retrying atomic copy as non-atomic

pipe_iov_copy_{from,to}_user() may be tried twice with the same iovec,
the first time atomically and the second time not.  The second attempt
needs to continue from the iovec position, pipe buffer offset and
remaining length where the first attempt failed, but currently the
pipe buffer offset and remaining length are reset.  This will corrupt
the piped data (possibly also leading to an information leak between
processes) and may also corrupt kernel memory.

This was fixed upstream by commits f0d1bec9d58d ("new helper:
copy_page_from_iter()") and 637b58c2887e ("switch pipe_read() to
copy_page_to_iter()"), but those aren't suitable for stable.  This fix
for older kernel versions was made by Seth Jennings for RHEL and I
have extracted it from their update.

CVE-2015-1805

(cherry picked from commit f7ebfe91b806501808413c8473a300dff58ddbb5)

Bug: 27275324

Change-Id: I459adb9076fcd50ff1f1c557089c4e421b036ec4
References: https://bugzilla.redhat.com/show_bug.cgi?id=1202855
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>