releases/4.19.41/net-stmmac-fix-dropping-of-multi-descriptor-rx-frame.patch

   1 From 0b582038c010f4b31b632314d7879350eed6ca4a Mon Sep 17 00:00:00 2001
   2 From: Aaro Koskinen <aaro.koskinen@nokia.com>
   3 Date: Wed, 27 Mar 2019 22:35:39 +0200
   4 Subject: net: stmmac: fix dropping of multi-descriptor RX frames
   5
   6 [ Upstream commit 8ac0c24fe1c256af6644caf3d311029440ec2fbd ]
   7
   8 Packets without the last descriptor set should be dropped early. If we
   9 receive a frame larger than the DMA buffer, the HW will continue using the
  10 next descriptor. Driver mistakes these as individual frames, and sometimes
  11 a truncated frame (without the LD set) may look like a valid packet.
  12
  13 This fixes a strange issue where the system replies to 4098-byte ping
  14 although the MTU/DMA buffer size is set to 4096, and yet at the same
  15 time it's logging an oversized packet.
  16
  17 Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
  18 Signed-off-by: David S. Miller <davem@davemloft.net>
  19 Signed-off-by: Sasha Levin <sashal@kernel.org>
  20 ---
  21  drivers/net/ethernet/stmicro/stmmac/enh_desc.c | 5 +++++
  22  1 file changed, 5 insertions(+)
  23
  24 diff --git a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
  25 index c42ef6c729c0..5202d6ad7919 100644
  26 --- a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
  27 +++ b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
  28 @@ -201,6 +201,11 @@ static int enh_desc_get_rx_status(void *data, struct stmmac_extra_stats *x,
  29         if (unlikely(rdes0 & RDES0_OWN))
  30                 return dma_own;
  31
  32 +       if (unlikely(!(rdes0 & RDES0_LAST_DESCRIPTOR))) {
  33 +               stats->rx_length_errors++;
  34 +               return discard_frame;
  35 +       }
  36 +
  37         if (unlikely(rdes0 & RDES0_ERROR_SUMMARY)) {
  38                 if (unlikely(rdes0 & RDES0_DESCRIPTOR_ERROR)) {
  39                         x->rx_desc++;
  40 --
  41 2.20.1
  42