r8169: Fix possible ring buffer corruption on fragmented Tx packets.

commit c71e3a5cffd5309d7f84444df03d5b72600cc417 upstream.

An issue was found on the RTL8125b when transmitting small fragmented
packets, whereby invalid entries were inserted into the transmit ring
buffer, subsequently leading to calls to dma_unmap_single() with a null
address.

This was caused by rtl8169_start_xmit() not noticing changes to nr_frags
which may occur when small packets are padded (to work around hardware
quirks) in rtl8169_tso_csum_v2().

To fix this, postpone inspecting nr_frags until after any padding has been
applied.

Fixes: 9020845fb5d6 ("r8169: improve rtl8169_start_xmit")
Cc: stable@vger.kernel.org
Signed-off-by: Ken Milmore <ken.milmore@gmail.com>
Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/27ead18b-c23d-4f49-a020-1fc482c5ac95@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 97b1fe71905f03af2336446b056faf1092b763a9..70d0b32395cdea273d806dd509e043988ff3d907 100644 (file)
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -4221,11 +4221,11 @@ static void rtl8169_doorbell(struct rtl8169_private *tp)
 static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
                                      struct net_device *dev)
 {
-       unsigned int frags = skb_shinfo(skb)->nr_frags;
        struct rtl8169_private *tp = netdev_priv(dev);
        unsigned int entry = tp->cur_tx % NUM_TX_DESC;
        struct TxDesc *txd_first, *txd_last;
        bool stop_queue, door_bell;
+       unsigned int frags;
        u32 opts[2];
 
        if (unlikely(!rtl_tx_slots_avail(tp))) {
@@ -4248,6 +4248,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
 
        txd_first = tp->TxDescArray + entry;
 
+       frags = skb_shinfo(skb)->nr_frags;
        if (frags) {
                if (rtl8169_xmit_frags(tp, skb, opts, entry))
                        goto err_dma_1;