Patch "sh_eth: fix NULL pointer dereference in sh_eth_ring_format()" has been added to the 4.4-stable tree

Patch "sh_eth: fix NULL pointer dereference in sh_eth_ring_format()" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    sh_eth: fix NULL pointer dereference in sh_eth_ring_format()

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sh_eth-fix-null-pointer-dereference-in-sh_eth_ring_format.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Sat Apr 16 10:02:53 PDT 2016
From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Date: Tue, 8 Mar 2016 01:36:28 +0300
Subject: sh_eth: fix NULL pointer dereference in sh_eth_ring_format()

From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.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@sang-engineering.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
@@ -1212,7 +1212,8 @@ 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_edmac(mdp, RD_RDLE);
+	if (rxdesc)
+		rxdesc->status |= cpu_to_edmac(mdp, RD_RDLE);
 
 	memset(mdp->tx_ring, 0, tx_ringsize);
 


Patches currently in stable-queue which might be from sergei.shtylyov@cogentembedded.com are

queue-4.4/sh_eth-fix-null-pointer-dereference-in-sh_eth_ring_format.patch
queue-4.4/sh_eth-advance-rxdesc-later-in-sh_eth_ring_format.patch