From 9337c54401a5bb6ac3c9f6c71dd2a9130cfba82e Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Wed, 11 Jun 2025 14:40:04 +0200 Subject: [PATCH] veth: prevent NULL pointer dereference in veth_xdp_rcv The veth peer device is RCU protected, but when the peer device gets deleted (veth_dellink) then the pointer is assigned NULL (via RCU_INIT_POINTER). This patch adds a necessary NULL check in veth_xdp_rcv when accessing the veth peer net_device. This fixes a bug introduced in commit dc82a33297fc ("veth: apply qdisc backpressure on full ptr_ring to reduce TX drops"). The bug is a race and only triggers when having inflight packets on a veth that is being deleted. Reported-by: Ihor Solodrai Closes: https://lore.kernel.org/all/fecfcad0-7a16-42b8-bff2-66ee83a6e5c4@linux.dev/ Reported-by: syzbot+c4c7bf27f6b0c4bd97fe@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/683da55e.a00a0220.d8eae.0052.GAE@google.com/ Fixes: dc82a33297fc ("veth: apply qdisc backpressure on full ptr_ring to reduce TX drops") Signed-off-by: Jesper Dangaard Brouer Acked-by: Ihor Solodrai Link: https://patch.msgid.link/174964557873.519608.10855046105237280978.stgit@firesoul Signed-off-by: Jakub Kicinski --- drivers/net/veth.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/veth.c b/drivers/net/veth.c index e58a0f1b5c5b..a3046142cb8e 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -909,7 +909,7 @@ static int veth_xdp_rcv(struct veth_rq *rq, int budget, /* NAPI functions as RCU section */ peer_dev = rcu_dereference_check(priv->peer, rcu_read_lock_bh_held()); - peer_txq = netdev_get_tx_queue(peer_dev, queue_idx); + peer_txq = peer_dev ? netdev_get_tx_queue(peer_dev, queue_idx) : NULL; for (i = 0; i < budget; i++) { void *ptr = __ptr_ring_consume(&rq->xdp_ring); @@ -959,7 +959,7 @@ static int veth_xdp_rcv(struct veth_rq *rq, int budget, rq->stats.vs.xdp_packets += done; u64_stats_update_end(&rq->stats.syncp); - if (unlikely(netif_tx_queue_stopped(peer_txq))) + if (peer_txq && unlikely(netif_tx_queue_stopped(peer_txq))) netif_tx_wake_queue(peer_txq); return done; -- 2.25.1