[PATCH net] net/packet: clear RX owner on VNET header error

[PATCH net] net/packet: clear RX owner on VNET header error

[Mark Amirkan via B4 Relay]

From: Mark Amirkan <markdamirkan@gmail.com>

Commit 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race
condition") added rx_owner_map and made tpacket_rcv() claim a V1 or V2
ring slot before converting the virtio-net header.  If the conversion
fails, the drop path leaves the slot claimed.

With a one-frame TPACKET_V2 ring, an unsupported UDP GSO packet leaves
the only slot unavailable, so the ring also drops the next valid packet.

Clear the ownership bit on this error path.  TPACKET_V3 already clears
its block state here.

Fixes: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition")
Cc: stable@vger.kernel.org
Assisted-by: Symbolic
Signed-off-by: Mark Amirkan <markdamirkan@gmail.com>
---
 net/packet/af_packet.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 76bde7906d..50cae32ae2 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2384,7 +2384,9 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	    virtio_net_hdr_from_skb(skb, h.raw + macoff -
 				    sizeof(struct virtio_net_hdr),
 				    vio_le(), true, 0)) {
-		if (po->tp_version == TPACKET_V3)
+		if (po->tp_version <= TPACKET_V2)
+			__clear_bit(slot_id, po->rx_ring.rx_owner_map);
+		else
 			prb_clear_blk_fill_status(&po->rx_ring);
 		goto drop_n_account;
 	}

---
base-commit: e6b6078ea1731b05b3b552497b3bce4bf8b014ae
change-id: 20260913-b4-send-packet-vnet-32b47964a7cf

Best regards,
--  
Mark Amirkan <markdamirkan@gmail.com>

Re: [PATCH net] net/packet: clear RX owner on VNET header error

[Willem de Bruijn]

Mark Amirkan via B4 Relay wrote:
> From: Mark Amirkan <markdamirkan@gmail.com>
> 
> Commit 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race
> condition") added rx_owner_map and made tpacket_rcv() claim a V1 or V2
> ring slot before converting the virtio-net header.  If the conversion
> fails, the drop path leaves the slot claimed.
> 
> With a one-frame TPACKET_V2 ring, an unsupported UDP GSO packet leaves
> the only slot unavailable, so the ring also drops the next valid packet.
> 
> Clear the ownership bit on this error path.  TPACKET_V3 already clears
> its block state here.
> 
> Fixes: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition")
> Cc: stable@vger.kernel.org
> Assisted-by: Symbolic
> Signed-off-by: Mark Amirkan <markdamirkan@gmail.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>