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cgroup: fix cgroup_write_event_control()

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81eeaf0411 ("cgroup: make cftype->[un]register_event() deal with
cgroup_subsys_state inst ead of cgroup") updated the cftype event
methods to take @css (cgroup_subsys_state) instead of @cgroup;
however, it incorrectly used @css passed to
cgroup_write_event_control(), which the dummy_css for the cgroup as
the file is a cgroup core file.  This leads to oops on event
registration.

Fix it by using the css matching the event target file.  Note that
cgroup_write_event_control() now disallows cgroup core files from
being event sources.  This is for simplicity and doesn't matter as
cgroup_event will be moved and made specific to memcg.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-08-15 11:43:15 -04:00
parent 0bfb4aa67c
commit 6e6eab0efd
1 changed files with 21 additions and 4 deletions
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25
kernel/cgroup.c
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@ -4040,10 +4040,10 @@ static void cgroup_event_ptable_queue_proc(struct file *file,
* Input must be in format '<event_fd> <control_fd> <args>'.
* Interpretation of args is defined by control file implementation.
*/
static int cgroup_write_event_control(struct cgroup_subsys_state *css,
static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
struct cftype *cft, const char *buffer)
{
struct cgroup *cgrp = css->cgroup;
struct cgroup *cgrp = dummy_css->cgroup;
struct cgroup_event *event;
struct cgroup *cgrp_cfile;
unsigned int efd, cfd;
@ -4065,7 +4065,7 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
event = kzalloc(sizeof(*event), GFP_KERNEL);
if (!event)
return -ENOMEM;
event->css = css;
INIT_LIST_HEAD(&event->list);
init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
@ -4101,6 +4101,23 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
goto out_put_cfile;
}
if (!event->cft->ss) {
ret = -EBADF;
goto out_put_cfile;
}
/* determine the css of @cfile and associate @event with it */
rcu_read_lock();
ret = -EINVAL;
event->css = cgroup_css(cgrp, event->cft->ss->subsys_id);
if (event->css)
ret = 0;
rcu_read_unlock();
if (ret)
goto out_put_cfile;
/*
* The file to be monitored must be in the same cgroup as
* cgroup.event_control is.
@ -4116,7 +4133,7 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
goto out_put_cfile;
}
ret = event->cft->register_event(css, event->cft,
ret = event->cft->register_event(event->css, event->cft,
event->eventfd, buffer);
if (ret)
goto out_put_cfile;