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Date: Sat, 28 Oct 2017 11:07:28 +0800 From: Li Bin <huawei.libin@...wei.com> To: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com> CC: <linux-kernel@...r.kernel.org>, <tanxiaofei@...wei.com>, <guohanjun@...wei.com>, <huawei.libin@...wei.com> Subject: [PATCH v2] workqueue: Fix NULL pointer dereference When queue_work() is used in irq (not in task context), there is a potential case that trigger NULL pointer dereference. ---------------------------------------------------------------- worker_thread() |-spin_lock_irq() |-process_one_work() |-worker->current_pwq = pwq |-spin_unlock_irq() |-worker->current_func(work) |-spin_lock_irq() |-worker->current_pwq = NULL |-spin_unlock_irq() //interrupt here |-irq_handler |-__queue_work() //assuming that the wq is draining |-is_chained_work(wq) |-current_wq_worker() //Here, 'current' is the interrupted worker! |-current->current_pwq is NULL here! |-schedule() ---------------------------------------------------------------- Avoid it by checking for task context in current_wq_worker(), and if not in task context, we shouldn't use the 'current' to check the condition. Reported-by: Xiaofei Tan <tanxiaofei@...wei.com> Signed-off-by: Li Bin <huawei.libin@...wei.com> --- kernel/workqueue_internal.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h index 8635417..29fa81f 100644 --- a/kernel/workqueue_internal.h +++ b/kernel/workqueue_internal.h @@ -9,6 +9,7 @@ #include <linux/workqueue.h> #include <linux/kthread.h> +#include <linux/preempt.h> struct worker_pool; @@ -59,7 +60,7 @@ struct worker { */ static inline struct worker *current_wq_worker(void) { - if (current->flags & PF_WQ_WORKER) + if (in_task() && (current->flags & PF_WQ_WORKER)) return kthread_data(current); return NULL; } -- 1.7.12.4
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