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 <[email protected]>
---
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);
--
2.25.1
Hello:
This patch was applied to netdev/net.git (refs/heads/master):
On Sun, 28 Mar 2021 00:30:29 -0700 you wrote:
> 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.
>
> [...]
Here is the summary with links:
- net:tipc: Fix a double free in tipc_sk_mcast_rcv
https://git.kernel.org/netdev/net/c/6bf24dc0cc0c
You are awesome, thank you!
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