Subject: [PATCH] e1000: do not allow watchdog to reenable transmits on shutdown

From: Marcelo Tosatti <[email-masked]>
Date: Thu, 6 Mar 2014 23:04:20 -0300

There is a race on the shutdown path of the e1000 driver
that allows the card to DMA into free'd memory.

The symptoms are similar to those described at 
commit d5bc77a223b0e9b9dfb002048d2b34a79e7d0b48,
"e1000: don't enable dma receives until after dma address has been
setup", where memory corruption is visible due to E1000_RXD_STAT_DD
being written to the DMA transfer descriptor.

Fix by not allowing the watchdog and tx fifo stall detector
to re-enable E1000_TCTL_EN.

Signed-off-by: Marcelo Tosatti <[email-masked]>

diff --git a/drivers/net/ethernet/intel/e1000/e1000.h b/drivers/net/ethernet/intel/e1000/e1000.h
index 10a0f22..bb5dc1a 100644
--- a/drivers/net/ethernet/intel/e1000/e1000.h
+++ b/drivers/net/ethernet/intel/e1000/e1000.h
@@ -321,7 +321,8 @@ struct e1000_adapter {
 enum e1000_state_t {
 	__E1000_TESTING,
 	__E1000_RESETTING,
-	__E1000_DOWN
+	__E1000_DOWN,
+	__E1000_NOTX = 4,
 };
 
 #undef pr_fmt
diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 46e6544..b20ce98 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -414,6 +414,7 @@ int e1000_up(struct e1000_adapter *adapter)
 	e1000_configure(adapter);
 
 	clear_bit(__E1000_DOWN, &adapter->flags);
+	clear_bit(__E1000_NOTX, &adapter->flags);
 
 	napi_enable(&adapter->napi);
 
@@ -524,6 +525,10 @@ void e1000_down(struct e1000_adapter *adapter)
 
 	netif_tx_disable(netdev);
 
+	/* do not allow watchdog to reenable transmits between 
+           clearing E1000_TCTL_EN below and setting E1000_DOWN */
+	set_bit(__E1000_NOTX, &adapter->flags);
+
 	/* disable transmits in the hardware */
 	tctl = er32(TCTL);
 	tctl &= ~E1000_TCTL_EN;
@@ -2339,6 +2344,9 @@ static void e1000_82547_tx_fifo_stall_task(struct work_struct *work)
 	struct net_device *netdev = adapter->netdev;
 	u32 tctl;
 
+	if (test_bit(__E1000_NOTX, &adapter->flags))
+		return;
+
 	if (atomic_read(&adapter->tx_fifo_stall)) {
 		if ((er32(TDT) == er32(TDH)) &&
 		   (er32(TDFT) == er32(TDFH)) &&
@@ -2412,6 +2420,9 @@ static void e1000_watchdog(struct work_struct *work)
 	struct e1000_tx_ring *txdr = adapter->tx_ring;
 	u32 link, tctl;
 
+	if (test_bit(__E1000_NOTX, &adapter->flags))
+		return;
+
 	link = e1000_has_link(adapter);
 	if ((netif_carrier_ok(netdev)) && link)
 		goto link_up;

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