Subject: Re: [PATCH net] ixgbe: fix crash with empty VF macvlan list

From: Simon Horman <[email-masked]>
Date: Fri, 6 Oct 2023 15:24:45 +0200

On Fri, Oct 06, 2023 at 03:49:39PM +0300, Dan Carpenter wrote:
> On Fri, Oct 06, 2023 at 01:16:27PM +0200, Simon Horman wrote:
> > On Thu, Oct 05, 2023 at 04:57:02PM +0300, Dan Carpenter wrote:
> > > The adapter->vf_mvs.l list needs to be initialized even if the list is
> > > empty.  Otherwise it will lead to crashes.
> > > 
> > > Fixes: c6bda30a06d9 ("ixgbe: Reconfigure SR-IOV Init")
> > 
> > Hi Dan,
> > 
> > I see that the patch cited above added the line you are changing.
> > But it also seems to me that patch was moving it from elsewhere.
> > 
> > Perhaps I am mistaken, but I wonder if this is a better tag.
> > 
> > Fixes: a1cbb15c1397 ("ixgbe: Add macvlan support for VF")
> > 
> 
> Yeah.  You're right.  I'll resend.

Thanks!

> > > Signed-off-by: Dan Carpenter <[email-masked]>
> > > ---
> > >  drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
> > > index a703ba975205..9cfdfa8a4355 100644
> > > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
> > > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_sriov.c
> > > @@ -28,6 +28,9 @@ static inline void ixgbe_alloc_vf_macvlans(struct ixgbe_adapter *adapter,
> > >  	struct vf_macvlans *mv_list;
> > >  	int num_vf_macvlans, i;
> > >  
> > > +	/* Initialize list of VF macvlans */
> > > +	INIT_LIST_HEAD(&adapter->vf_mvs.l);
> > > +
> > >  	num_vf_macvlans = hw->mac.num_rar_entries -
> > >  			  (IXGBE_MAX_PF_MACVLANS + 1 + num_vfs);
> > >  	if (!num_vf_macvlans)
> > > @@ -36,8 +39,6 @@ static inline void ixgbe_alloc_vf_macvlans(struct ixgbe_adapter *adapter,
> > >  	mv_list = kcalloc(num_vf_macvlans, sizeof(struct vf_macvlans),
> > >  			  GFP_KERNEL);
> > >  	if (mv_list) {
> > 
> > I'm not sure it it is worth it, but perhaps more conventional error
> > handling could be used here:
> > 
> > 	if (!mv_list)
> > 		return;
> > 
> > 	for (i = 0; i < num_vf_macvlans; i++) {
> > 		...
> 
> I mean error handling is always cleaner than success handling but it's
> probably not worth cleaning up in old code.  I say it's not worth
> cleaning up old code and yet I secretly reversed two if statements like
> this yesterday.  :P
> https://lore.kernel.org/all/[email-masked]/
> It really is nicer, yes.  But it just makes the patch too noisy.

Yeah, I'm also worried about the noise in this case.