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

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

[Julia Lawall]

From: Julia Lawall <julia@diku.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@diku.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);
 		}

Re: [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

[Vitaly Bordug]

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On Mon, 12 May 2008 15:38:26 +0200 (CEST)
Julia Lawall wrote:

> From: Julia Lawall <julia@diku.dk>
Acked-by: Vitaly Bordug <vitb@kernel.crashing.org>

> 
> 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@diku.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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Re: [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

[Francois Romieu]

Julia Lawall <julia@diku.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);
>  		}

Extra cookies for the nice soul who:
- removes the 'if (registered)' test (it can not happen)
- uses different error lablels and unrolls the error path. I can not claim
  that the current error path is wrong but it would not hurt if it was more
  trivially balanced.

-- 
Ueimor

Re: [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

[Scott Wood]

Francois Romieu wrote:
> Julia Lawall <julia@diku.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);
>>  		}
> 
> Extra cookies for the nice soul who:
> - removes the 'if (registered)' test (it can not happen)
> - uses different error lablels and unrolls the error path. I can not claim
>   that the current error path is wrong but it would not hurt if it was more
>   trivially balanced.
> 

Please note that this code is going away very soon, when arch/ppc dies.

-Scott

Re: [PATCH 4/6] drivers/net/fs_enet: remove null pointer dereference

[Jeff Garzik]

Julia Lawall wrote:
> From: Julia Lawall <julia@diku.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@diku.dk>

applied