netdev - [PATCH v2 2/3] tg3: Fix tx_pending check for MAX_SKB

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Date:	Thu, 21 Aug 2014 14:57:19 -0700
From:	Benjamin Poirier <bpoirier@...e.de>
To:	Prashant Sreedharan <prashant@...adcom.com>,
	Michael Chan <mchan@...adcom.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] tg3: Fix tx_pending check for MAX_SKB_FRAGS

The rest of the driver assumes at least one free descriptor in the tx ring.
Therefore, since an skb with max frags takes up (MAX_SKB_FRAGS + 1)
descriptors, tx_pending must be > (MAX_SKB_FRAGS + 1).

Signed-off-by: Benjamin Poirier <bpoirier@...e.de>
---
Changes v1->v2
Moved ahead in the series from 3/3 to 2/3, no functionnal change

I reproduced this bug using the same approach explained in patch 1.
The bug reproduces with tx_pending = 18

---
 drivers/net/ethernet/broadcom/tg3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index b11c0fd..0cecd6d 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -12319,7 +12319,7 @@ static int tg3_set_ringparam(struct net_device *dev, struct ethtool_ringparam *e
 	if ((ering->rx_pending > tp->rx_std_ring_mask) ||
 	    (ering->rx_jumbo_pending > tp->rx_jmb_ring_mask) ||
 	    (ering->tx_pending > TG3_TX_RING_SIZE - 1) ||
-	    (ering->tx_pending <= MAX_SKB_FRAGS) ||
+	    (ering->tx_pending <= MAX_SKB_FRAGS + 1) ||
 	    (tg3_flag(tp, TSO_BUG) &&
 	     (ering->tx_pending <= (MAX_SKB_FRAGS * 3))))
 		return -EINVAL;
-- 
1.8.4.5

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