diff options
authorSergio Valverde <>2016-07-01 11:44:30 -0600
committerDavid S. Miller <>2016-07-02 14:48:14 -0400
commit373819ec391de0d11f63b10b2fb69ef2854236ca (patch)
parenta8b7d7709dc6db7d6d8a9a04aa9d49b029a27203 (diff)
enc28j60: Fix race condition in enc28j60 driver
The interrupt worker code for the enc28j60 relies only on the TXIF flag to determinate if the packet transmission was completed. However the datasheet specifies in section 12.1.3 that TXERIF will clear the TXRTS after a transmit abort. Also in section 12.1.4 that TXIF will be set when TXRTS transitions from '1' to '0'. Therefore the TXIF flag is enabled during transmission errors. This causes a race condition, since the worker code will invoke enc28j60_tx_clear() -> netif_wake_queue(), potentially invoking the ndo_start_xmit function to send a new packet. The enc28j60_send_packet function uses a workqueue that invokes enc28j60_hw_tx(). In between this function is called, the worker from the interrupt handler will enter the path for error handler because of the TXERIF flag, causing to invoke enc28j60_tx_clear() again and releasing the packet scheduled for transmission, causing a kernel crash with due a NULL pointer. These crashes due a NULL pointer were observed under stress conditions of the device. A BUG_ON() sequence was used to validate the issue was fixed, and has been running without problems for 2 years now. Signed-off-by: Diego Dompe <> Acked-by: Sergio Valverde <> Signed-off-by: David S. Miller <>
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/net/ethernet/microchip/enc28j60.c b/drivers/net/ethernet/microchip/enc28j60.c
index 7066954c39d6..0a26b11ca8f6 100644
--- a/drivers/net/ethernet/microchip/enc28j60.c
+++ b/drivers/net/ethernet/microchip/enc28j60.c
@@ -1151,7 +1151,8 @@ static void enc28j60_irq_work_handler(struct work_struct *work)
enc28j60_phy_read(priv, PHIR);
/* TX complete handler */
- if ((intflags & EIR_TXIF) != 0) {
+ if (((intflags & EIR_TXIF) != 0) &&
+ ((intflags & EIR_TXERIF) == 0)) {
bool err = false;
if (netif_msg_intr(priv))
@@ -1203,7 +1204,7 @@ static void enc28j60_irq_work_handler(struct work_struct *work)
enc28j60_tx_clear(ndev, true);
} else
enc28j60_tx_clear(ndev, true);
- locked_reg_bfclr(priv, EIR, EIR_TXERIF);
+ locked_reg_bfclr(priv, EIR, EIR_TXERIF | EIR_TXIF);
/* RX Error handler */
if ((intflags & EIR_RXERIF) != 0) {
@@ -1238,6 +1239,8 @@ static void enc28j60_irq_work_handler(struct work_struct *work)
static void enc28j60_hw_tx(struct enc28j60_net *priv)
+ BUG_ON(!priv->tx_skb);
if (netif_msg_tx_queued(priv))
": Tx Packet Len:%d\n", priv->tx_skb->len);