[PATCH v2 net 2/6] net: enetc: linearize PTP event packets with one-step TX timestamping

[Vladimir Oltean <vladimir.oltean@nxp.com>]

Sashiko reports that enetc_ptp_parse() uses ptp_parse_header(), which
does not handle fragmented headers, and expects the entire area between
skb_mac_header() and the end of the PTP header to be linear.

When the driver fails to parse a fragmented PTP frame to find the
offsets to the originTimestamp and correctionField, it falls back to
two-step timestamping, which is technically not what user space asked
for, and it may not be prepared to receive the timestamped packet
through the socket error queue.

The problem can be avoided relatively easily by linearizing packets with
one-step timestamping requests prior to calling enetc_ptp_parse(). These
are infrequent enough that this should not be a performance problem.

Fixes: 7294380c5211 ("enetc: support PTP Sync packet one-step timestamping")
Link: https://sashiko.dev/#/patchset/20260401172246.1075883-1-vladimir.oltean%40nxp.com
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
v1->v2: patch is new
---
 drivers/net/ethernet/freescale/enetc/enetc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index ece10a58d44e..ac6cad5605e4 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -1059,6 +1059,11 @@ netdev_tx_t enetc_xmit(struct sk_buff *skb, struct net_device *ndev)
 
 	/* Fall back to two-step timestamp if not one-step Sync packet */
 	if (enetc_cb->flag & ENETC_F_TX_ONESTEP_SYNC_TSTAMP) {
+		if (unlikely(skb_linearize(skb))) {
+			dev_kfree_skb_any(skb);
+			return NETDEV_TX_OK;
+		}
+
 		if (enetc_ptp_parse(skb, &udp, &msgtype, &twostep,
 				    &offset1, &offset2) ||
 		    msgtype != PTP_MSGTYPE_SYNC || twostep != 0) {
-- 
2.43.0