Commit-ID: 068c5cc5ac7414a8e9eb7856b4bf3cc4d4744267
Gitweb: http://git.kernel.org/tip/068c5cc5ac7414a8e9eb7856b4bf3cc4d4744267
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 19 Jan 2011 12:26:11 +0100
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 19 Jan 2011 12:51:32 +0100
sched, cgroup: Use exit hook to avoid use-after-free crash
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 <vmiklos@xxxxxxxxxxxxxx>
Fixed-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
LKML-Reference: <1293206353.29444.205.camel@laptop>
---
kernel/sched.c | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 0a169a8..fa5272a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -606,6 +606,9 @@ static inline struct task_group *task_group(struct task_struct *p)
struct task_group *tg;
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));
tg = container_of(css, struct task_group, css);
@@ -8880,6 +8883,20 @@ cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
}
}
+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)
@@ -8952,6 +8969,7 @@ 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,
--
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