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

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Message-ID: <12b96a9f-27c7-86b4-af90-cad594240bf8@oracle.com>
Date:   Mon, 23 Sep 2019 21:34:50 +0530
From:   Allen <allen.pais@...cle.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/net/fjes: fix a potential NULL pointer
 dereference


> 
> 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