[PATCH] drivers/net/fjes: fix a potential NULL pointer dereference

[PATCH] drivers/net/fjes: fix a potential NULL pointer dereference

[Allen Pais]

alloc_workqueue is not checked for errors and as a result,
a potential NULL dereference could occur.

Signed-off-by: Allen Pais <allen.pais@oracle.com>
---
 drivers/net/fjes/fjes_main.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/fjes/fjes_main.c b/drivers/net/fjes/fjes_main.c
index bbbc1dc..2d04104 100644
--- a/drivers/net/fjes/fjes_main.c
+++ b/drivers/net/fjes/fjes_main.c
@@ -1237,8 +1237,15 @@ static int fjes_probe(struct platform_device *plat_dev)
 	adapter->open_guard = false;
 
 	adapter->txrx_wq = alloc_workqueue(DRV_NAME "/txrx", WQ_MEM_RECLAIM, 0);
+	if (unlikely(!adapter->txrx_wq))
+		goto err_free_netdev;
+
 	adapter->control_wq = alloc_workqueue(DRV_NAME "/control",
 					      WQ_MEM_RECLAIM, 0);
+	if (unlikely(!adapter->control_wq)) {
+		destroy_workqueue(adapter->txrx_wq);
+		goto err_free_netdev;
+	}
 
 	INIT_WORK(&adapter->tx_stall_task, fjes_tx_stall_task);
 	INIT_WORK(&adapter->raise_intr_rxdata_task,
-- 
1.9.1

Re: [PATCH] drivers/net/fjes: fix a potential NULL pointer dereference

[Jakub Kicinski]

On Wed, 18 Sep 2019 22:03:15 +0530, Allen Pais wrote:
> alloc_workqueue is not checked for errors and as a result,
> a potential NULL dereference could occur.
> 
> Signed-off-by: Allen Pais <allen.pais@oracle.com>

If I'm looking at this right you are jumping to err_free_netdev without
setting the err variable. It must had been set to 0 from the return of
fjes_sw_init(). This means we will free the netdev, and return 0. This 
means probe will not fail and driver's remove function will be run
at some point. fjes_remove it will try to free the netdev again.

Looks like there's another existing bug here in that the work queues
are not free when something fails in fjes_probe, just the netdev.

Once you untangle that, and before you post a v2, could you please try
to identify which commit introduced the regression and provide an
appropriate "Fixes" tag?

> diff --git a/drivers/net/fjes/fjes_main.c b/drivers/net/fjes/fjes_main.c
> index bbbc1dc..2d04104 100644
> --- a/drivers/net/fjes/fjes_main.c
> +++ b/drivers/net/fjes/fjes_main.c
> @@ -1237,8 +1237,15 @@ static int fjes_probe(struct platform_device *plat_dev)
>  	adapter->open_guard = false;
>  
>  	adapter->txrx_wq = alloc_workqueue(DRV_NAME "/txrx", WQ_MEM_RECLAIM, 0);
> +	if (unlikely(!adapter->txrx_wq))
> +		goto err_free_netdev;
> +
>  	adapter->control_wq = alloc_workqueue(DRV_NAME "/control",
>  					      WQ_MEM_RECLAIM, 0);
> +	if (unlikely(!adapter->control_wq)) {
> +		destroy_workqueue(adapter->txrx_wq);
> +		goto err_free_netdev;
> +	}
>  
>  	INIT_WORK(&adapter->tx_stall_task, fjes_tx_stall_task);
>  	INIT_WORK(&adapter->raise_intr_rxdata_task,

Re: [PATCH] drivers/net/fjes: fix a potential NULL pointer dereference

[Allen]

> 
> If I'm looking at this right you are jumping to err_free_netdev without
> setting the err variable. It must had been set to 0 from the return of
> fjes_sw_init(). This means we will free the netdev, and return 0. This
> means probe will not fail and driver's remove function will be run
> at some point. fjes_remove it will try to free the netdev again.

  Good catch. Here's a quick diff what I should have done,

--- a/drivers/net/fjes/fjes_main.c
+++ b/drivers/net/fjes/fjes_main.c
@@ -1236,9 +1236,21 @@ static int fjes_probe(struct platform_device 
*plat_dev)
         adapter->force_reset = false;
         adapter->open_guard = false;

+       /* Re-initialize err to -ENOMEM to handle workqueue allocation 
failures,
+          and we don't return 0 on failure.
+       */
+       err = -ENOMEM;
+
         adapter->txrx_wq = alloc_workqueue(DRV_NAME "/txrx", 
WQ_MEM_RECLAIM, 0);
+       if (unlikely(!adapter->txrx_wq))
+               goto err_free_netdev;
+
         adapter->control_wq = alloc_workqueue(DRV_NAME "/control",
                                               WQ_MEM_RECLAIM, 0);
+       if (unlikely(!adapter->control_wq)) {
+               destroy_workqueue(adapter->txrx_wq);
+               goto err_free_netdev;
+       }


> Looks like there's another existing bug here in that the work queues
> are not free when something fails in fjes_probe, just the netdev.

I shall look into it and send out a separate fix.

> Once you untangle that, and before you post a v2, could you please try
> to identify which commit introduced the regression and provide an
> appropriate "Fixes" tag?
> 

Fixes: f2edc4e1b078("net: fjes: fjes_main: Remove create_workqueue")

- Allen