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

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Message-ID: <569ba96b-2bc3-45ea-b397-36e7ef88ed8f@kadam.mountain>
Date: Fri, 6 Oct 2023 15:49:39 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Simon Horman <horms@...nel.org>
Cc: Greg Rose <gregory.v.rose@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] ixgbe: fix crash with empty VF macvlan list

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.


> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> > ---
> >  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/d9da4c97-0da9-499f-9a21-1f8e3f148dc1@moroto.mountain/
It really is nicer, yes.  But it just makes the patch too noisy.

regards,
dan carpenter