2016-12-02 10:50:26 +00:00
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From edfa1131e425e0dafe9561fee792a0d319fa734e Mon Sep 17 00:00:00 2001
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2016-09-10 12:54:26 +00:00
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From: Sergio Valverde <sergio.valverde@hpe.com>
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Date: Fri, 1 Jul 2016 11:44:30 -0600
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Subject: [PATCH] enc28j60: Fix race condition in enc28j60 driver
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(Upstream commit 373819ec391de0d11f63b10b2fb69ef2854236ca)
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The interrupt worker code for the enc28j60 relies only on the TXIF flag to
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determinate if the packet transmission was completed. However the datasheet
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specifies in section 12.1.3 that TXERIF will clear the TXRTS after a
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transmit abort. Also in section 12.1.4 that TXIF will be set
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when TXRTS transitions from '1' to '0'. Therefore the TXIF flag is enabled
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during transmission errors.
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This causes a race condition, since the worker code will invoke
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enc28j60_tx_clear() -> netif_wake_queue(), potentially invoking the
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ndo_start_xmit function to send a new packet. The enc28j60_send_packet function
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uses a workqueue that invokes enc28j60_hw_tx(). In between this function is
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called, the worker from the interrupt handler will enter the path for error
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handler because of the TXERIF flag, causing to invoke enc28j60_tx_clear() again
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and releasing the packet scheduled for transmission, causing a kernel crash with
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due a NULL pointer.
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These crashes due a NULL pointer were observed under stress conditions of the
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device. A BUG_ON() sequence was used to validate the issue was fixed, and has
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been running without problems for 2 years now.
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Signed-off-by: Diego Dompe <dompe@hpe.com>
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Acked-by: Sergio Valverde <sergio.valverde@hpe.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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drivers/net/ethernet/microchip/enc28j60.c | 7 +++++--
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1 file changed, 5 insertions(+), 2 deletions(-)
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--- a/drivers/net/ethernet/microchip/enc28j60.c
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+++ b/drivers/net/ethernet/microchip/enc28j60.c
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@@ -1147,7 +1147,8 @@ static void enc28j60_irq_work_handler(st
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enc28j60_phy_read(priv, PHIR);
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}
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/* TX complete handler */
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- if ((intflags & EIR_TXIF) != 0) {
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+ if (((intflags & EIR_TXIF) != 0) &&
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+ ((intflags & EIR_TXERIF) == 0)) {
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bool err = false;
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loop++;
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if (netif_msg_intr(priv))
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@@ -1199,7 +1200,7 @@ static void enc28j60_irq_work_handler(st
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enc28j60_tx_clear(ndev, true);
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} else
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enc28j60_tx_clear(ndev, true);
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- locked_reg_bfclr(priv, EIR, EIR_TXERIF);
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+ locked_reg_bfclr(priv, EIR, EIR_TXERIF | EIR_TXIF);
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}
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/* RX Error handler */
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if ((intflags & EIR_RXERIF) != 0) {
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@@ -1234,6 +1235,8 @@ static void enc28j60_irq_work_handler(st
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*/
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static void enc28j60_hw_tx(struct enc28j60_net *priv)
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{
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+ BUG_ON(!priv->tx_skb);
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+
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if (netif_msg_tx_queued(priv))
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printk(KERN_DEBUG DRV_NAME
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": Tx Packet Len:%d\n", priv->tx_skb->len);
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