netdev - [PATCH net-next 3/5] usbnet: ipheth: drop RX URBs with no payload

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Message-ID: <20240806172809.675044-3-forst@pen.gy>
Date: Tue,  6 Aug 2024 19:28:07 +0200
From: Foster Snowhill <forst@....gy>
To: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Georgi Valkov <gvalkov@...il.com>,
	Oliver Neukum <oneukum@...e.com>,
	netdev@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: [PATCH net-next 3/5] usbnet: ipheth: drop RX URBs with no payload

On iPhone 15 Pro Max one can observe periodic URBs with no payload
on the "bulk in" (RX) endpoint. These don't seem to do anything
meaningful. Reproduced on iOS 17.5.1 and 17.6.

This behaviour isn't observed on iPhone 11 on the same iOS version. The
nature of these zero-length URBs is so far unknown.

Drop RX URBs with no payload.

Signed-off-by: Foster Snowhill <forst@....gy>
---
 drivers/net/usb/ipheth.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c
index 017255615508..f04c7bf79665 100644
--- a/drivers/net/usb/ipheth.c
+++ b/drivers/net/usb/ipheth.c
@@ -286,6 +286,12 @@ static void ipheth_rcvbulk_callback(struct urb *urb)
 		return;
 	}
 
+	/* iPhone may periodically send URBs with no payload
+	 * on the "bulk in" endpoint. It is safe to ignore them.
+	 */
+	if (urb->actual_length == 0)
+		goto rx_submit;
+
 	/* RX URBs starting with 0x00 0x01 do not encapsulate Ethernet frames,
 	 * but rather are control frames. Their purpose is not documented, and
 	 * they don't affect driver functionality, okay to drop them.
-- 
2.45.1