Groups > linux.kernel > #1194682

Re: [PATCH] user_ns: use correct check for single-threadedness

From	Andrew Morton <akpm@linux-foundation.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] user_ns: use correct check for single-threadedness
Date	2015-07-28 23:40 +0200
Message-ID	<pRkLn-4Fc-1@gated-at.bofh.it> (permalink)
References	<pRgHM-7lh-27@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Tue, 28 Jul 2015 10:15:00 -0700 Kees Cook <keescook@chromium.org> wrote:

> From: Ricky Zhou <rickyz@chromium.org>
> 
> Checking mm_users > 1 does not mean a process is multithreaded. For
> example, reading /proc/PID/maps temporarily increments mm_users, allowing
> other processes to (accidentally) interfere with unshare() calls.
> 
> This fixes observed failures of unshare(CLONE_NEWUSER) incorrectly
> returning EINVAL if another processes happened to be simultaneously
> reading the maps file.

Yikes.  current_is_single_threaded() is expensive.  Are we sure this
isn't going to kill someone's workload?

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH] user_ns: use correct check for single-threadedness Andrew Morton <akpm@linux-foundation.org> - 2015-07-28 23:40 +0200
  Re: [PATCH] user_ns: use correct check for single-threadedness Kees Cook <keescook@chromium.org> - 2015-07-29 00:00 +0200

csiph-web