This is a note to let you know that I've just added the patch titled
sched, cgroup: Use exit hook to avoid use-after-free crash
to the 2.6.37-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-cgroup-use-exit-hook-to-avoid-use-after-free-crash.patch
and it can be found in the queue-2.6.37 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 068c5cc5ac7414a8e9eb7856b4bf3cc4d4744267 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <[email protected]>
Date: Wed, 19 Jan 2011 12:26:11 +0100
Subject: sched, cgroup: Use exit hook to avoid use-after-free crash
From: Peter Zijlstra <[email protected]>
commit 068c5cc5ac7414a8e9eb7856b4bf3cc4d4744267 upstream.
By not notifying the controller of the on-exit move back to
init_css_set, we fail to move the task out of the previous
cgroup's cfs_rq. This leads to an opportunity for a
cgroup-destroy to come in and free the cgroup (there are no
active tasks left in it after all) to which the not-quite dead
task is still enqueued.
Reported-by: Miklos Vajna <[email protected]>
Fixed-by: Mike Galbraith <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Mike Galbraith <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
LKML-Reference: <1293206353.29444.205.camel@laptop>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -607,6 +607,9 @@ static inline struct task_group *task_gr
{
struct cgroup_subsys_state *css;
+ if (p->flags & PF_EXITING)
+ return &root_task_group;
+
css = task_subsys_state_check(p, cpu_cgroup_subsys_id,
lockdep_is_held(&task_rq(p)->lock));
return container_of(css, struct task_group, css);
@@ -9178,6 +9181,20 @@ cpu_cgroup_attach(struct cgroup_subsys *
}
}
+static void
+cpu_cgroup_exit(struct cgroup_subsys *ss, struct task_struct *task)
+{
+ /*
+ * cgroup_exit() is called in the copy_process() failure path.
+ * Ignore this case since the task hasn't ran yet, this avoids
+ * trying to poke a half freed task state from generic code.
+ */
+ if (!(task->flags & PF_EXITING))
+ return;
+
+ sched_move_task(task);
+}
+
#ifdef CONFIG_FAIR_GROUP_SCHED
static int cpu_shares_write_u64(struct cgroup *cgrp, struct cftype *cftype,
u64 shareval)
@@ -9250,6 +9267,7 @@ struct cgroup_subsys cpu_cgroup_subsys =
.destroy = cpu_cgroup_destroy,
.can_attach = cpu_cgroup_can_attach,
.attach = cpu_cgroup_attach,
+ .exit = cpu_cgroup_exit,
.populate = cpu_cgroup_populate,
.subsys_id = cpu_cgroup_subsys_id,
.early_init = 1,
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.37/workqueue-relax-lockdep-annotation-on-flush_work.patch
queue-2.6.37/sched-cgroup-use-exit-hook-to-avoid-use-after-free-crash.patch
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