linux-kernel - [PATCH] ns83820: Avoid bad pointer deref in ns83820_init

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Message-ID: <alpine.LNX.2.00.1101172116330.27021@swampdragon.chaosbits.net>
Date:	Mon, 17 Jan 2011 21:24:57 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	netdev@...r.kernel.org
cc:	linux-ns83820@...ck.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, Tejun Heo <tj@...nel.org>,
	Kulikov Vasiliy <segooon@...il.com>,
	Denis Kirjanov <dkirjanov@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Benjamin LaHaise <bcrl@...ck.org>
Subject: [PATCH] ns83820: Avoid bad pointer deref in ns83820_init_one().

In drivers/net/ns83820.c::ns83820_init_one() we dynamically allocate 
memory via alloc_etherdev(). We then call PRIV() on the returned storage 
which is 'return netdev_priv()'. netdev_priv() takes the pointer it is 
passed and adds 'ALIGN(sizeof(struct net_device), NETDEV_ALIGN)' to it and 
returns it. Then we test the resulting pointer for NULL, which it is 
unlikely to be at this point, and later dereference it. This will go bad 
if alloc_etherdev() actually returned NULL.

This patch reworks the code slightly so that we test for a NULL pointer 
(and return -ENOMEM) directly after calling alloc_etherdev().

Signed-off-by: Jesper Juhl <jj@...osbits.net>
---
 ns83820.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

  Compile tested only. I have no way to test this for real.

diff --git a/drivers/net/ns83820.c b/drivers/net/ns83820.c
index 84134c7..a41b2cf 100644
--- a/drivers/net/ns83820.c
+++ b/drivers/net/ns83820.c
@@ -1988,12 +1988,11 @@ static int __devinit ns83820_init_one(struct pci_dev *pci_dev,
 	}

 	ndev = alloc_etherdev(sizeof(struct ns83820));
-	dev = PRIV(ndev);
-
 	err = -ENOMEM;
-	if (!dev)
+	if (!ndev)
 		goto out;

+	dev = PRIV(ndev);
 	dev->ndev = ndev;

 	spin_lock_init(&dev->rx_info.lock);

-- 
Jesper Juhl <jj@...osbits.net>            http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please.

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