tree 8fe20ac83fe10f806d6736231de04c497964cc34
parent 638a77430ff9175390925e3f370ae8259d55ca2d
author Ben Hutchings <ben@decadent.org.uk> 1434489066 +0100
committer Patrick Tjin <pattjin@google.com> 1458243707 -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

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>
(cherry picked from commit 85c34d007116f8a8aafb173966a605fb03532f45)