diff options
| author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2009-01-07 18:07:39 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-08 08:31:02 -0800 |
| commit | 77efecd9e0526327548152df715ab8644ecb5ba0 (patch) | |
| tree | 4dd2a82fe5db454fb018e434e07c3e6f30dc9832 | |
| parent | 104cbd55377029e70fc2cee01089e84b9c36e5dc (diff) | |
cgroups: call find_css_set() safely in cgroup_attach_task()
In cgroup_attach_task(), tsk maybe exit when we call find_css_set(). and
find_css_set() will access to invalid css_set.
This patch increases the count before get_css_set(), and decreases it
after find_css_set().
NOTE:
css_set's refcount is also taskcount, after this patch applied, taskcount
may be off-by-one WHEN cgroup_lock() is not held. but I reviewed other
code which use taskcount, they are still correct. No regression found by
reviewing and simply testing.
So I do not use two counters in css_set. (one counter for taskcount, the
other for refcount. like struct mm_struct) If this fix cause regression,
we will use two counters in css_set.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/cgroup.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 00d5136d38c..61e92c5867e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1214,7 +1214,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) int retval = 0; struct cgroup_subsys *ss; struct cgroup *oldcgrp; - struct css_set *cg = tsk->cgroups; + struct css_set *cg; struct css_set *newcg; struct cgroupfs_root *root = cgrp->root; int subsys_id; @@ -1234,11 +1234,16 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) } } + task_lock(tsk); + cg = tsk->cgroups; + get_css_set(cg); + task_unlock(tsk); /* * Locate or allocate a new css_set for this task, * based on its final set of cgroups */ newcg = find_css_set(cg, cgrp); + put_css_set(cg); if (!newcg) return -ENOMEM; |