cpuset: fix cpuset_print_task_mems_allowed() vs rename() race
rename() will change dentry->d_name. The result of this race can be worse than seeing partially rewritten name, but we might access a stale pointer because rename() will re-allocate memory to hold a longer name. It's safe in the protection of dentry->d_lock. v2: check NULL dentry before acquiring dentry lock. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
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@ -2511,8 +2511,16 @@ void cpuset_print_task_mems_allowed(struct task_struct *tsk)
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dentry = task_cs(tsk)->css.cgroup->dentry;
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dentry = task_cs(tsk)->css.cgroup->dentry;
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spin_lock(&cpuset_buffer_lock);
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spin_lock(&cpuset_buffer_lock);
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snprintf(cpuset_name, CPUSET_NAME_LEN,
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dentry ? (const char *)dentry->d_name.name : "/");
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if (!dentry) {
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strcpy(cpuset_name, "/");
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} else {
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spin_lock(&dentry->d_lock);
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strlcpy(cpuset_name, (const char *)dentry->d_name.name,
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CPUSET_NAME_LEN);
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spin_unlock(&dentry->d_lock);
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}
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nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN,
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nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN,
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tsk->mems_allowed);
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tsk->mems_allowed);
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printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n",
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printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n",
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