commit: 068c5cc5ac7414a8e9eb7856b4bf3cc4d4744267 From: Peter Zijlstra <[email protected]> Date: Wed, 19 Jan 2011 12:26:11 +0100 Subject: [PATCH] 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 <[email protected]> Fixed-by: Mike Galbraith <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Cc: <[email protected]> Cc: Mike Galbraith <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> 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, _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
