net/sonic: Fix receive buffer replenishment

As soon as the driver is finished with a receive buffer it allocs a new
one and overwrites the corresponding RRA entry with a new buffer pointer.

Problem is, the buffer pointer is split across two word-sized registers.
It can't be updated in one atomic store. So this operation races with the
chip while it stores received packets and advances its RRP register.
This could result in memory corruption by a DMA write.

Avoid this problem by adding buffers only at the location given by the
RWP register, in accordance with the National Semiconductor datasheet.

Re-factor this code into separate functions to calculate a RRA pointer
and to update the RWP.

Fixes: efcce839360f ("[PATCH] macsonic/jazzsonic network drivers update")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/net/ethernet/natsemi/sonic.h b/drivers/net/ethernet/natsemi/sonic.h
index e6d47e45c5c2..cc2f7b4b77e3 100644
--- a/drivers/net/ethernet/natsemi/sonic.h
+++ b/drivers/net/ethernet/natsemi/sonic.h
@@ -314,8 +314,6 @@ struct sonic_local {
 	u32 rda_laddr;              /* logical DMA address of RDA */
 	dma_addr_t rx_laddr[SONIC_NUM_RRS]; /* logical DMA addresses of rx skbuffs */
 	dma_addr_t tx_laddr[SONIC_NUM_TDS]; /* logical DMA addresses of tx skbuffs */
-	unsigned int rra_end;
-	unsigned int cur_rwp;
 	unsigned int cur_rx;
 	unsigned int cur_tx;           /* first unacked transmit packet */
 	unsigned int eol_rx;
@@ -450,6 +448,22 @@ static inline __u16 sonic_rra_get(struct net_device* dev, int entry,
 			     (entry * SIZEOF_SONIC_RR) + offset);
 }
 
+static inline u16 sonic_rr_addr(struct net_device *dev, int entry)
+{
+	struct sonic_local *lp = netdev_priv(dev);
+
+	return lp->rra_laddr +
+	       entry * SIZEOF_SONIC_RR * SONIC_BUS_SCALE(lp->dma_bitmode);
+}
+
+static inline u16 sonic_rr_entry(struct net_device *dev, u16 addr)
+{
+	struct sonic_local *lp = netdev_priv(dev);
+
+	return (addr - (u16)lp->rra_laddr) / (SIZEOF_SONIC_RR *
+					      SONIC_BUS_SCALE(lp->dma_bitmode));
+}
+
 static const char version[] =
     "sonic.c:v0.92 20.9.98 tsbogend@alpha.franken.de\n";