On Thu, Dec 31, 2015 at 03:08:53PM +0900, Tetsuo Handa wrote:

Willy Tarreau wrote:

quoted

On Wed, Dec 30, 2015 at 09:58:42AM +0100, Hannes Frederic Sowa wrote:

quoted

The MSG_PEEK code should not be harmful and the patch is good as is. I 
first understood from the published private thread, that it is possible 
for a program to exceed the rlimit of fds. But the DoS is only by 
keeping the fds in flight and not attaching them to any program.

Exactly. The real issue is when these FDs become very expensive such as
pipes full of data.

As you wrote how to abuse this vulnerability which exists in Linux 2.0
and later kernel, I quote a short description from private thread.

  "an unprivileged user consumes all file descriptors so that other
  unprivileged user cannot work" and "an unprivileged user consumes all
  kernel memory so that the OOM killer kills almost all processes before
  the culprit process is killed (CVE-2013-4312)".

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Mitigates: CVE-2013-4312 (Linux 2.0+)

Well I didn't reveal any secret as it was publicly reported first
in 2010, it's only that Mark sent us the proof of concept exploit
on the security list recently :-)

    https://bugzilla.kernel.org/show_bug.cgi?id=20402

Anyway I'll resend the patch with your reported-by, the CVE and
Hannes' ACK.

Thanks!
Willy