Messages in this thread Patch in this message | | | Date | Fri, 21 Nov 2008 16:49:20 +0800 | From | Lai Jiangshan <> | Subject | [PATCH] cgroups: fix cgroup_iter_next() bug. |
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we access to res->cgroups without the task_lock(), so res->cgroups may be changed. it's unreliable, and "if (l == &res->cgroups->tasks)" may be false forever.
we don't need add any lock for fixing this bug. we just access to struct css_set by struct cg_cgroup_link, not by struct task_struct.
since we hold css_set_lock, struct cg_cgroup_link is reliable.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 358e775..ddc10ac 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1810,6 +1819,7 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, { struct task_struct *res; struct list_head *l = it->task; + struct cg_cgroup_link *link; /* If the iterator cg is NULL, we have no tasks */ if (!it->cg_link) @@ -1817,7 +1827,8 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, res = list_entry(l, struct task_struct, cg_list); /* Advance iterator to find next entry */ l = l->next; - if (l == &res->cgroups->tasks) { + link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list); + if (l == &link->cg->tasks) { /* We reached the end of this task list - move on to * the next cg_cgroup_link */ cgroup_advance_iter(cgrp, it);
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