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

On Fri, Jul 31, 2026 9:51 PM, Simon Horman wrote:
> 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 <[email protected]>
> > ---
> >  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():

Looks like a bad time to clear the flag...
I'll change it to check pdev->msix_enabled but not the flag.

> 
>   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));
> >  }
> >
> >  /**
>