Re: [PATCH net] net: ngbe: fix NULL pointer dereference in non-MSI-X interrupt enabling

[Simon Horman <horms@kernel.org>]

On Tue, Jul 28, 2026 at 05:35:54PM +0800, Jiawen Wu wrote:
> In non-MSI-X mode (such as legacy INTx or single MSI), wx->msix_entry is
> not allocated or initialized. Calling NGBE_INTR_MISC(wx) dereferences
> wx->msix_entry->entry, leading to a NULL pointer dereference crash.
> 
> This issue was introduced by fixing the IRQ vector when the number of
> VFs is 7. Since macro NGBE_INTR_MISC is used in only one place and
> relies on MSI-X allocation, remove it.
> 
> Fix the issue by explicitly checking WX_FLAG_IRQ_VECTOR_SHARED to
> determine the correct vector index and using BIT() to convert it into
> the interrupt mask required by wx_intr_enable().
> 
> Fixes: 4174c0c331a2 ("net: ngbe: specify IRQ vector when the number of VFs is 7")
> Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
> ---
>  drivers/net/ethernet/wangxun/ngbe/ngbe_main.c | 4 +++-
>  drivers/net/ethernet/wangxun/ngbe/ngbe_type.h | 1 -
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c b/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
> index a16221995909..5d89fc84e8bc 100644
> --- a/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
> +++ b/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
> @@ -180,8 +180,10 @@ static void ngbe_irq_enable(struct wx *wx, bool queues)
>  	/* mask interrupt */
>  	if (queues)
>  		wx_intr_enable(wx, NGBE_INTR_ALL);
> +	else if (test_bit(WX_FLAG_IRQ_VECTOR_SHARED, wx->flags))
> +		wx_intr_enable(wx, BIT(0));

Hi Jiawen,

I am wondering if you could take a look over the following issue
which is included in the AI-generated review on sashiko.dev [1]

[1] https://sashiko.dev/#/patchset/21947C51A754F86C%2B20260728093554.9324-1-jiawenwu%40trustnetic.com

  Does this change introduce a desynchronization between the software state
  and the hardware configuration if SR-IOV enablement fails?

  If pci_enable_sriov() fails inside wx_pci_sriov_enable(), the error path
  clears the WX_FLAG_IRQ_VECTOR_SHARED flag via wx_sriov_clear_data():

  wx_pci_sriov_enable() {
      ...
      err = pci_enable_sriov(wx->pdev, num_vfs);
      if (err) {
          ...
          goto err_out;
      }
      ...
  err_out:
      wx_sriov_clear_data(wx);
      return err;
  }

  However, the hardware was already re-initialized with the MISC interrupt
  mapped to vector 0. Since the hardware configuration isn't reverted, won't
  subsequent shared interrupts cause the hardware to auto-mask vector 0, which
  will then never be unmasked here because the flag was cleared? This appears
  to result in a permanent masking of Queue 0 and MISC events.

>  	else
> -		wx_intr_enable(wx, NGBE_INTR_MISC(wx));
> +		wx_intr_enable(wx, BIT(wx->num_q_vectors));
>  }
>  
>  /**

...