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The queued skb keeps only a bare skb->dev pointer. If the originating netns is torn down before the workqueue callback runs, ip6_rcv_finish() can still dereference skb->dev after the device has already been released by default_device_exit_batch(). Fix this by taking a netdev reference when queueing the skb and dropping it after the reinject callback completes. This was reproduced with KASAN under QEMU: BUG: KASAN: slab-use-after-free in ip6_rcv_finish+0x17c/0x1b0 Workqueue: events xfrm_trans_reinject Call Trace: ip6_rcv_finish+0x17c/0x1b0 xfrm_trans_reinject+0x292/0x440 process_one_work+0x63c/0x1100 worker_thread+0x62d/0xef0 kthread+0x368/0x480 ret_from_fork+0x529/0x750 Allocated by task 112: alloc_netdev_mqs+0x82/0x1180 rtnl_create_link+0xaa4/0xe30 rtnl_newlink+0xa98/0x1f90 Freed by task 12: device_release+0x9b/0x210 netdev_run_todo+0x497/0xcf0 default_device_exit_batch+0x735/0xab0 cleanup_net+0x3c7/0x860 The issue can be reproduced by repeatedly: - creating an IPv6 veth pair and network namespace, - installing IPv6 transport-mode XFRM state and policy, - sending IPv6 traffic to queue async reinject work, and - tearing the namespace and device down in parallel. When unprivileged user namespaces are enabled, this can be triggered by a non-root user after entering its own user/net namespace with unshare -Urn. Fixes: acf568ee859f ("xfrm: Reinject transport-mode packets through tasklet") Cc: stable@vger.kernel.org Signed-off-by: Qi Tang --- net/xfrm/xfrm_input.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c index 4ed346e682c7..4b5147cb44b7 100644 --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -40,6 +40,7 @@ struct xfrm_trans_cb { } header; int (*finish)(struct net *net, struct sock *sk, struct sk_buff *skb); struct net *net; + struct net_device *dev; }; #define XFRM_TRANS_SKB_CB(__skb) ((struct xfrm_trans_cb *)&((__skb)->cb[0])) @@ -784,9 +785,13 @@ static void xfrm_trans_reinject(struct work_struct *work) spin_unlock_bh(&trans->queue_lock); local_bh_disable(); - while ((skb = __skb_dequeue(&queue))) - XFRM_TRANS_SKB_CB(skb)->finish(XFRM_TRANS_SKB_CB(skb)->net, - NULL, skb); + while ((skb = __skb_dequeue(&queue))) { + struct xfrm_trans_cb *cb = XFRM_TRANS_SKB_CB(skb); + struct net_device *dev = cb->dev; + + cb->finish(cb->net, NULL, skb); + dev_put(dev); + } local_bh_enable(); } @@ -805,6 +810,8 @@ int xfrm_trans_queue_net(struct net *net, struct sk_buff *skb, XFRM_TRANS_SKB_CB(skb)->finish = finish; XFRM_TRANS_SKB_CB(skb)->net = net; + XFRM_TRANS_SKB_CB(skb)->dev = skb->dev; + dev_hold(XFRM_TRANS_SKB_CB(skb)->dev); spin_lock_bh(&trans->queue_lock); __skb_queue_tail(&trans->queue, skb); spin_unlock_bh(&trans->queue_lock); -- 2.43.0