linux-kernel - [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

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Message-ID: <Pine.LNX.4.64.0805121537590.3694@ask.diku.dk>
Date:	Mon, 12 May 2008 15:38:26 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	pantelis.antoniou@...il.com, vbordug@...mvista.com,
	linuxppc-dev@...abs.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

From: Julia Lawall <julia@...u.dk>

The following code appears in the function fs_init_instance in the file drivers/net/fs_enet/fs_enet-main.c.

	if (fep->ops == NULL) {
		printk(KERN_ERR DRV_MODULE_NAME
		       ": %s No matching ops found (%d).\n",
		       ndev->name, fpi->fs_no);
		err = -EINVAL;
		goto err;
	}

This code implies that at the point of err, fep->ops can be NULL, so an
extra test is needed before dereferencing this value.


This problem was found using the following semantic match
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression E, E1;
identifier f;
statement S1,S2,S3;
@@

* if (E == NULL)
{
  ... when != if (E == NULL) S1 else S2
      when != E = E1
* E->f
  ... when any
  return ...;
}
else S3
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---

diff -u -p a/drivers/net/fs_enet/fs_enet-main.c b/drivers/net/fs_enet/fs_enet-main.c
--- a/drivers/net/fs_enet/fs_enet-main.c	2008-04-27 11:41:11.000000000 +0200
+++ b/drivers/net/fs_enet/fs_enet-main.c	2008-05-12 09:41:52.000000000 +0200
@@ -1093,7 +1093,7 @@ err:
 		if (registered)
 			unregister_netdev(ndev);
 
-		if (fep != NULL) {
+		if (fep && fep->ops) {
 			(*fep->ops->free_bd)(ndev);
 			(*fep->ops->cleanup_data)(ndev);
 		}
--
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