From 6bf24dc0cc0cc43b29ba344b66d78590e687e046 Mon Sep 17 00:00:00 2001 From: Lv Yunlong Date: Sun, 28 Mar 2021 00:30:29 -0700 Subject: [PATCH] net:tipc: Fix a double free in tipc_sk_mcast_rcv In the if(skb_peek(arrvq) == skb) branch, it calls __skb_dequeue(arrvq) to get the skb by skb = skb_peek(arrvq). Then __skb_dequeue() unlinks the skb from arrvq and returns the skb which equals to skb_peek(arrvq). After __skb_dequeue(arrvq) finished, the skb is freed by kfree_skb(__skb_dequeue(arrvq)) in the first time. Unfortunately, the same skb is freed in the second time by kfree_skb(skb) after the branch completed. My patch removes kfree_skb() in the if(skb_peek(arrvq) == skb) branch, because this skb will be freed by kfree_skb(skb) finally. Fixes: cb1b728096f54 ("tipc: eliminate race condition at multicast reception") Signed-off-by: Lv Yunlong Signed-off-by: David S. Miller --- net/tipc/socket.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/tipc/socket.c b/net/tipc/socket.c index cebcc104dc70..022999e0202d 100644 --- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -1265,7 +1265,7 @@ void tipc_sk_mcast_rcv(struct net *net, struct sk_buff_head *arrvq, spin_lock_bh(&inputq->lock); if (skb_peek(arrvq) == skb) { skb_queue_splice_tail_init(&tmpq, inputq); - kfree_skb(__skb_dequeue(arrvq)); + __skb_dequeue(arrvq); } spin_unlock_bh(&inputq->lock); __skb_queue_purge(&tmpq);