From: Tjerk Kusters When Rx hardware timestamping is enabled (e.g. ptp4l, which configures HWTSTAMP_FILTER_ALL), the NIC prepends a 16-byte timestamp header to the first Rx buffer of every received frame. igb_clean_rx_irq() strips this header inside its per-buffer loop: if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) { ts_hdr_len = igb_ptp_rx_pktstamp(rx_ring->q_vector, pktbuf, ×tamp); pkt_offset += ts_hdr_len; size -= ts_hdr_len; } For a frame that spans more than one Rx buffer (e.g. a jumbo frame), this block runs once per buffer. The timestamp header only exists at the start of the first buffer, but igb_ptp_rx_pktstamp() is called for every buffer. On a continuation buffer the data is packet payload, not a timestamp header. igb_ptp_rx_pktstamp() already has two guards against acting on a non-header buffer: it returns 0 if PTP is disabled, and returns 0 if the reserved dwords (the first 8 bytes) are non-zero. Neither is sufficient here: PTP is enabled, and a continuation buffer whose payload happens to begin with 8 zero bytes passes the reserved-dword check. In that case the payload is mistaken for a valid timestamp header and igb_ptp_rx_pktstamp() returns IGB_TS_HDR_LEN, so the caller strips 16 bytes of real data from that buffer. A frame spanning N buffers whose continuation buffers start with zero bytes therefore loses 16 * (N - 1) bytes from its tail. This is easily triggered by a GigE Vision camera streaming dark frames (mostly 0x00 pixel data) over jumbo UDP with PTP active on the receiver: the all-zero frames arrive truncated while frames with non-zero content are fine. There is no error indication. No content-based check can reliably tell a continuation buffer that begins with zero bytes from a real timestamp header, because both are all zero. Fix it structurally instead: only attempt the strip on the first buffer of a frame, which is the only buffer that can contain a timestamp header. In igb_clean_rx_irq() skb is NULL until the first buffer has been processed, so guarding the strip with !skb restricts it to the first buffer regardless of payload content. Fixes: 5379260852b0 ("igb: Fix XDP with PTP enabled") Cc: stable@vger.kernel.org Reviewed-by: Piotr Kwapulinski Reviewed-by: Aleksandr Loktionov Reviewed-by: Kurt Kanzenbach Signed-off-by: Tjerk Kusters Tested-by: Alexander Nowlin Signed-off-by: Tony Nguyen --- drivers/net/ethernet/intel/igb/igb_main.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index d4a897a8c82c..5c09dc4a2566 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -9069,8 +9069,11 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget) rx_buffer = igb_get_rx_buffer(rx_ring, size, &rx_buf_pgcnt); pktbuf = page_address(rx_buffer->page) + rx_buffer->page_offset; - /* pull rx packet timestamp if available and valid */ - if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) { + /* pull rx packet timestamp if available and valid; it is only + * present on the first buffer of a frame + */ + if (!skb && + igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) { int ts_hdr_len; ts_hdr_len = igb_ptp_rx_pktstamp(rx_ring->q_vector, -- 2.47.1