linux-kernel - [PATCH] xfrm_input: Protect queue with lock

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Date:   Mon,  9 Sep 2019 10:37:00 +0200
From:   Joerg Vehlow <lkml@...coder.de>
To:     linux-kernel@...r.kernel.org, joerg.vehlow@...-tech.de
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH] xfrm_input: Protect queue with lock

From: Joerg Vehlow <joerg.vehlow@...-tech.de>

During the skb_queue_splice_init the tasklet could have been preempted
and __skb_queue_tail called, which led to an inconsistent queue.

Signed-off-by: Joerg Vehlow <joerg.vehlow@...-tech.de>
---
 net/xfrm/xfrm_input.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 790b514f86b6..4c4e669fcd16 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -512,12 +512,15 @@ EXPORT_SYMBOL(xfrm_input_resume);
 
 static void xfrm_trans_reinject(unsigned long data)
 {
+	unsigned long flags;
 	struct xfrm_trans_tasklet *trans = (void *)data;
 	struct sk_buff_head queue;
 	struct sk_buff *skb;
 
 	__skb_queue_head_init(&queue);
+	spin_lock_irqsave(&trans->queue.lock, flags);
 	skb_queue_splice_init(&trans->queue, &queue);
+	spin_unlock_irqrestore(&trans->queue.lock, flags);
 
 	while ((skb = __skb_dequeue(&queue)))
 		XFRM_TRANS_SKB_CB(skb)->finish(dev_net(skb->dev), NULL, skb);
@@ -535,7 +538,7 @@ int xfrm_trans_queue(struct sk_buff *skb,
 		return -ENOBUFS;
 
 	XFRM_TRANS_SKB_CB(skb)->finish = finish;
-	__skb_queue_tail(&trans->queue, skb);
+	skb_queue_tail(&trans->queue, skb);
 	tasklet_schedule(&trans->tasklet);
 	return 0;
 }
@@ -560,7 +563,7 @@ void __init xfrm_input_init(void)
 		struct xfrm_trans_tasklet *trans;
 
 		trans = &per_cpu(xfrm_trans_tasklet, i);
-		__skb_queue_head_init(&trans->queue);
+		skb_queue_head_init(&trans->queue);
 		tasklet_init(&trans->tasklet, xfrm_trans_reinject,
 			     (unsigned long)trans);
 	}
-- 
2.20.1