[PATCH 1/2] sh_eth: fix NULL pointer dereference in sh_eth_ring_format()

[Sergei Shtylyov]

In a low memory situation, if netdev_alloc_skb() fails on a first RX ring
loop iteration  in sh_eth_ring_format(), 'rxdesc' is still NULL.  Avoid
kernel oops by adding the 'rxdesc' check after the loop.

Reported-by: Wolfram Sang <wsa+rene...@sang-engineering.com>
Signed-off-by: Sergei Shtylyov <sergei.shtyl...@cogentembedded.com>

---
 drivers/net/ethernet/renesas/sh_eth.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: net/drivers/net/ethernet/renesas/sh_eth.c
===================================================================
--- net.orig/drivers/net/ethernet/renesas/sh_eth.c
+++ net/drivers/net/ethernet/renesas/sh_eth.c
@@ -1163,7 +1163,8 @@ static void sh_eth_ring_format(struct ne
        mdp->dirty_rx = (u32) (i - mdp->num_rx_ring);
 
        /* Mark the last entry as wrapping the ring. */
-       rxdesc->status |= cpu_to_le32(RD_RDLE);
+       if (rxdesc)
+               rxdesc->status |= cpu_to_le32(RD_RDLE);
 
        memset(mdp->tx_ring, 0, tx_ringsize);