netdev - [PATCH 04/10] net/macb: Fix a race in macb_start

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <40f02ee50a29aaec6c949432a1bcf09f4b027181.1346775479.git.nicolas.ferre@atmel.com>
Date:	Wed, 5 Sep 2012 10:19:11 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	<netdev@...r.kernel.org>
CC:	<linux-arm-kernel@...ts.infradead.org>, <davem@...emloft.net>,
	<havard@...nnemoen.net>, <nicolas.ferre@...el.com>,
	<plagnioj@...osoft.com>, <jamie@...ieiles.com>,
	<linux-kernel@...r.kernel.org>, <patrice.vilchez@...el.com>
Subject: [PATCH 04/10] net/macb: Fix a race in macb_start_xmit()

From: Havard Skinnemoen <havard@...nnemoen.net>

Fix a race in macb_start_xmit() where we unconditionally set the TSTART bit.
If an underrun just happened (we do this with interrupts disabled, so it might
not have been handled yet), the controller starts transmitting from the first
entry in the ring, which is usually wrong.
Restart the controller after error handling.

Signed-off-by: Havard Skinnemoen <havard@...nnemoen.net>
[nicolas.ferre@...el.com: split patch in topics]
Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
---
 drivers/net/ethernet/cadence/macb.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 2228dfc..f4b8adf 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -390,6 +390,13 @@ static void macb_tx(struct macb *bp)
 		dev_kfree_skb_irq(skb);
 	}
 
+	/*
+	 * Someone may have submitted a new frame while this interrupt
+	 * was pending, or we may just have handled an error.
+	 */
+	if (head != tail && !(status & MACB_BIT(TGO)))
+		macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
+
 	bp->tx_tail = tail;
 	if (netif_queue_stopped(bp->dev) &&
 	    TX_BUFFS_AVAIL(bp) > MACB_TX_WAKEUP_THRESH)
@@ -696,7 +703,18 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	skb_tx_timestamp(skb);
 
-	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
+	/*
+	 * Only start the controller if the queue was empty; otherwise
+	 * we may race against the hardware resetting the ring pointer
+	 * due to a transmit error.
+	 *
+	 * If the controller is idle but the queue isn't empty, there
+	 * must be a pending interrupt that will trigger as soon as we
+	 * re-enable interrupts, and the interrupt handler will make
+	 * sure the controler is started.
+	 */
+	if (NEXT_TX(bp->tx_tail) == bp->tx_head)
+		macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
 
 	if (TX_BUFFS_AVAIL(bp) < 1)
 		netif_stop_queue(dev);
-- 
1.7.10

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html