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Subject[PATCH 5.5 024/151] net/packet: tpacket_rcv: do not increment ring index on drop
Date
From: Willem de Bruijn <willemb@google.com>

[ Upstream commit 46e4c421a053c36bf7a33dda2272481bcaf3eed3 ]

In one error case, tpacket_rcv drops packets after incrementing the
ring producer index.

If this happens, it does not update tp_status to TP_STATUS_USER and
thus the reader is stalled for an iteration of the ring, causing out
of order arrival.

The only such error path is when virtio_net_hdr_from_skb fails due
to encountering an unknown GSO type.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/packet/af_packet.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2273,6 +2273,13 @@ static int tpacket_rcv(struct sk_buff *s
TP_STATUS_KERNEL, (macoff+snaplen));
if (!h.raw)
goto drop_n_account;
+
+ if (do_vnet &&
+ virtio_net_hdr_from_skb(skb, h.raw + macoff -
+ sizeof(struct virtio_net_hdr),
+ vio_le(), true, 0))
+ goto drop_n_account;
+
if (po->tp_version <= TPACKET_V2) {
packet_increment_rx_head(po, &po->rx_ring);
/*
@@ -2285,12 +2292,6 @@ static int tpacket_rcv(struct sk_buff *s
status |= TP_STATUS_LOSING;
}

- if (do_vnet &&
- virtio_net_hdr_from_skb(skb, h.raw + macoff -
- sizeof(struct virtio_net_hdr),
- vio_le(), true, 0))
- goto drop_n_account;
-
po->stats.stats1.tp_packets++;
if (copy_skb) {
status |= TP_STATUS_COPY;

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