| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <1323227914.5057.10.camel@marge.simson.net>
Date: Wed, 07 Dec 2011 04:18:34 +0100
From: Mike Galbraith <efault@....de>
To: David Rientjes <rientjes@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Paul Menage <paul@...lmenage.org>,
LKML <linux-kernel@...r.kernel.org>,
Tejun Heo <htejun@...il.com>, Li Zefan <lizf@...fujitsu.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [resubmit] Re: [patch-final] Re: patch] cpusets, cgroups: disallow
attaching kthreadd
On Tue, 2011-12-06 at 15:53 -0800, David Rientjes wrote:
> Mike, would you mind resending the patch for the fourth or fifth time? If
> not, I'll rebase it.
Sure, below are the two candidates. I like Peter's idea better (door
#2), "Keep yer grubby mitts offa _my_ Mom" is a natural reaction ;-)
Door #1
From: Mike Galbraith <efault@....de>
cpusets, cgroups: disallow attaching kthreadd
Allowing kthreadd to be moved to a non-root group makes no sense, it being
a global resource, and needlessly leads unsuspecting users toward trouble.
1. An RT workqueue worker thread spawned in a task group with no rt_runtime
allocated is not schedulable. Simple user error, but harmful to the box.
2. A worker thread which acquires PF_THREAD_BOUND can never leave a cpuset,
rendering the cpuset immortal.
Save the user some unexpected trouble, just say no.
Signed-off-by: Mike Galbraith <efault@....de>
Acked-by: David Rientjes <rientjes@...gle.com>
Acked-by: Paul Menage <paul@...lmenage.org>
---
kernel/cpuset.c | 6 ++++--
kernel/sched/core.c | 10 ++++++++++
2 files changed, 14 insertions(+), 2 deletions(-)
Index: linux-3.0-tip/kernel/cpuset.c
===================================================================
--- linux-3.0-tip.orig/kernel/cpuset.c
+++ linux-3.0-tip/kernel/cpuset.c
@@ -59,6 +59,7 @@
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/cgroup.h>
+#include <linux/kthread.h>
/*
* Workqueue for cpuset related tasks.
@@ -1385,9 +1386,10 @@ static int cpuset_can_attach(struct cgro
* set of allowed nodes is unnecessary. Thus, cpusets are not
* applicable for such threads. This prevents checking for success of
* set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may
- * be changed.
+ * be changed. We also disallow attaching kthreadd, to prevent it's
+ * child from becoming trapped should it then acquire PF_THREAD_BOUND.
*/
- if (tsk->flags & PF_THREAD_BOUND)
+ if (tsk->flags & PF_THREAD_BOUND || tsk == kthreadd_task)
return -EINVAL;
return 0;
Index: linux-3.0-tip/kernel/sched/core.c
===================================================================
--- linux-3.0-tip.orig/kernel/sched/core.c
+++ linux-3.0-tip/kernel/sched/core.c
@@ -71,6 +71,7 @@
#include <linux/ftrace.h>
#include <linux/slab.h>
#include <linux/init_task.h>
+#include <linux/kthread.h>
#include <asm/tlb.h>
#include <asm/irq_regs.h>
@@ -7461,6 +7462,15 @@ cpu_cgroup_destroy(struct cgroup_subsys
static int
cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
+ /*
+ * kthreadd can fork workers for an RT workqueue in a cgroup
+ * which may or may not have rt_runtime allocated. Just say no,
+ * as attaching a global resource to a non-root group doesn't
+ * make any sense anyway.
+ */
+ if (tsk == kthreadd_task)
+ return -EINVAL;
+
#ifdef CONFIG_RT_GROUP_SCHED
if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
return -EINVAL;
Door #2
From: Mike Galbraith <efault@....de>
cgroups: disallow attaching kthreadd
Allowing kthreadd to be moved to a non-root group makes no sense, it being
a global resource, and needlessly leads unsuspecting users toward trouble.
1. An RT workqueue worker thread spawned in a task group with no rt_runtime
allocated is not schedulable. Simple user error, but harmful to the box.
2. A worker thread which acquires PF_THREAD_BOUND can never leave a cpuset,
rendering the cpuset immortal.
Save the user some unexpected trouble, just say no.
Signed-off-by: Mike Galbraith <efault@....de>
---
kernel/cgroup.c | 9 +++++++++
1 file changed, 9 insertions(+)
Index: linux-3.0-tip/kernel/cgroup.c
===================================================================
--- linux-3.0-tip.orig/kernel/cgroup.c
+++ linux-3.0-tip/kernel/cgroup.c
@@ -60,6 +60,7 @@
#include <linux/eventfd.h>
#include <linux/poll.h>
#include <linux/flex_array.h> /* used in cgroup_attach_proc */
+#include <linux/kthread.h>
#include <linux/atomic.h>
@@ -1824,6 +1825,14 @@ int cgroup_attach_task(struct cgroup *cg
struct cgroup *oldcgrp;
struct cgroupfs_root *root = cgrp->root;
+ /*
+ * Workqueue threads may acquire PF_THREAD_BOUND and become
+ * trapped in a cpuset, or RT worker may be born in a cgroup
+ * with no rt_runtime allocated. Just say no.
+ */
+ if (tsk == kthreadd_task)
+ return -EINVAL;
+
/* Nothing to do if the task is already in that cgroup */
oldcgrp = task_cgroup_from_root(tsk, root);
if (cgrp == oldcgrp)
Door #3
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists