>From 994a762080e4b136171c82ac78f7d7bbf17a451d Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@xxxxxxxxxx>
Date: Wed, 14 Aug 2013 23:38:21 -0400
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.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 66d0107..ef93bfd 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4044,10 +4044,10 @@ 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;
@@ -4069,7 +4069,7 @@ 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);
@@ -4105,6 +4105,18 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
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);
+ 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.
@@ -4120,7 +4132,7 @@ 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;
--
1.8.3.1
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