Commit 9337c544 authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Jakub Kicinski
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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 dc82a332 ("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: default avatarIhor Solodrai <ihor.solodrai@linux.dev>
Closes: https://lore.kernel.org/all/fecfcad0-7a16-42b8-bff2-66ee83a6e5c4@linux.dev/


Reported-by: default avatar <syzbot+c4c7bf27f6b0c4bd97fe@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/683da55e.a00a0220.d8eae.0052.GAE@google.com/


Fixes: dc82a332 ("veth: apply qdisc backpressure on full ptr_ring to reduce TX drops")
Signed-off-by: default avatarJesper Dangaard Brouer <hawk@kernel.org>
Acked-by: default avatarIhor Solodrai <ihor.solodrai@linux.dev>
Link: https://patch.msgid.link/174964557873.519608.10855046105237280978.stgit@firesoul


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a844b0c8

drivers/net/veth.c

+2 −2
Original line number Diff line number Diff line
@@ -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;