linux-kernel - [PATCH 4.5 035/124] sh_eth: fix NULL pointer dereference in sh_eth_ring

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Date:	Mon, 18 Apr 2016 11:28:27 +0900
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.5 035/124] sh_eth: fix NULL pointer dereference in sh_eth_ring_format()

4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>

[ Upstream commit c1b7fca65070bfadca94dd53a4e6b71cd4f69715 ]

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+renesas@...g-engineering.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/renesas/sh_eth.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/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);