> -----Original Message-----
> From: Intel-wired-lan <[email protected]> On Behalf
> Of John Ousterhout
> Sent: Tuesday, May 12, 2026 8:20 PM
> To: [email protected]
> Cc: Nguyen, Anthony L <[email protected]>; intel-wired-
> [email protected]; Kitszel, Przemyslaw
> <[email protected]>; [email protected]; Keller, Jacob
> E <[email protected]>; John Ousterhout <[email protected]>
> Subject: [Intel-wired-lan] [PATCH net v3] ice: fix packet corruption
> due to extraneous page flip
>
> Consider the following sequence of events:
> * The bottom half of a buffer page is filled with data from
> packet A. The page has a net reference count (reference count
> - bias) of 1. The page is returned to the NIC, flipped to
> use the top half.
> * Before the reference on the page is released, the NIC returns
> the page with no data in it ('size' is zero in ice_clean_rx_irq).
> In this case the bias does not get decremented. The page still
> has a net reference count of 1, so it gets returned to the NIC.
> However, ice_put_rx_mbuf flipped the page so that the bottom
> half is active.
> * If the NIC stores another packet in the page before packet A
> has released its reference, the data in packet A will be
> overwritten with data from the new packet.
> * Unfortunately zero-length buffers occur frequently: they seem
> to occur whenever a packet uses every available byte in a
> buffer, ending precisely at the end of the buffer. When this
> happens the NIC seems to generate an extra zero-length
> buffer.
> The fix is for ice_put_rx_mbuf not to flip pages that have a size of
> 0.
>
> This patch applies directly to longterm stable versions 6.18.27 and
> 6.12.86; it also seems relevant for 6.6.137 but would need
> modifcations for that version. I have not examined earlier versions.
>
> Unfortunately there is no upstream commit id for this patch because
> the ICE driver has undergone a major revision (libeth refactor and
> pagepool conversion) that eliminated the buggy code. Thus the problem
> no longer exists in the main line.
>
> Cc: [email protected] # 6.12+
> Signed-off-by: John Ousterhout <[email protected]>
> ---
> drivers/net/ethernet/intel/ice/ice_txrx.c | 23 ++++++++++++++++++++--
> -
> 1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c
> b/drivers/net/ethernet/intel/ice/ice_txrx.c
> index 51c459a3e722..081c7a7392b7 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> @@ -1215,6 +1215,13 @@ static void ice_put_rx_mbuf(struct ice_rx_ring
> *rx_ring, struct xdp_buff *xdp,
> xdp_frags = xdp_get_shared_info_from_buff(xdp)-
> >nr_frags;
>
> while (idx != ntc) {
> + union ice_32b_rx_flex_desc *rx_desc;
> + unsigned int size;
> +
> + rx_desc = ICE_RX_DESC(rx_ring, idx);
> + size = le16_to_cpu(rx_desc->wb.pkt_len) &
> + ICE_RX_FLX_DESC_PKT_LEN_M;
> +
> buf = &rx_ring->rx_buf[idx];
> if (++idx == cnt)
> idx = 0;
> @@ -1224,10 +1231,20 @@ static void ice_put_rx_mbuf(struct ice_rx_ring
> *rx_ring, struct xdp_buff *xdp,
> * To do this, only adjust pagecnt_bias for fragments up
> to
> * the total remaining after the XDP program has run.
> */
> - if (verdict != ICE_XDP_CONSUMED)
> - ice_rx_buf_adjust_pg_offset(buf, xdp->frame_sz);
> - else if (i++ <= xdp_frags)
> + if (verdict != ICE_XDP_CONSUMED) {
> + /* Don't "flip" the page if size is 0: in this
> case
> + * the data in the current half will not be used
> so
> + * it's OK to reuse that half. And, since the
> bias
> + * didn't get decremented for this half, the page
> can
> + * be returned to the NIC even if the other half
> is
> + * still in use, so flipping the page could cause
> + * live packet data to be overwritten.
> + */
> + if (size != 0)
> + ice_rx_buf_adjust_pg_offset(buf, xdp-
> >frame_sz);
> + } else if (i++ <= xdp_frags) {
> buf->pagecnt_bias++;
> + }
>
> ice_put_rx_buf(rx_ring, buf);
> }
> --
> 2.43.0
Reviewed-by: Aleksandr Loktionov <[email protected]>
