[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 <redacted>
---
 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@chaosbits.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.

On Mon, Jan 17, 2011 at 09:24:57PM +0100, Jesper Juhl wrote:

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 <redacted>

Yeah, the previous code was a little bit ugly.
Good catch!

On Mon, Jan 17, 2011 at 09:24:57PM +0100, Jesper Juhl wrote:

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().

Looks good.

		-ben

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

From: Benjamin LaHaise <bcrl@kvack.org>
Date: Tue, 18 Jan 2011 11:42:00 -0500

On Mon, Jan 17, 2011 at 09:24:57PM +0100, Jesper Juhl wrote:

quoted

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().

Looks good.

		-ben

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>

Applied, thanks everyone.