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: stable@vger.kernel.org # 6.12+ Signed-off-by: John Ousterhout --- 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