netdev - Re: [PATCH] idpf: nullify pointers after they are freed

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Message-ID: <CAODvEq6NXpwYZbXiQeisYEE-sJaaG-tN1u-rq+RTSi=gPY+EAQ@mail.gmail.com>
Date: Fri, 23 Jan 2026 09:55:59 -0800
From: Li Li <boolli@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>, 
	Przemek Kitszel <przemyslaw.kitszel@...el.com>, "David S. Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, David Decotigny <decot@...gle.com>, 
	Anjali Singhai <anjali.singhai@...el.com>, Sridhar Samudrala <sridhar.samudrala@...el.com>, 
	Brian Vazquez <brianvv@...gle.com>, emil.s.tantilov@...el.com
Subject: Re: [PATCH] idpf: nullify pointers after they are freed

On Fri, Jan 23, 2026 at 1:19 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Fri, Jan 23, 2026 at 6:27 AM Li Li <boolli@...gle.com> wrote:
> >
> > rss_data->rss_key and vport->q_vector_idxs need to be nullified after
> > they are freed. Checks like "if (!rss_data->rss_key)" and
> > "if (!vport->q_vector_idxs)" in the code could fail if they are not
> > nullified.
> >
> > Tested: built and booted the kernel.
> >
> > Fixes: 83f38f210b85 ("idpf: Fix RSS LUT NULL pointer crash on early ethtool operations")
> > Fixes: 8a558cbda51b ("idpf: fix potential memory leak on kcalloc() failure")
> > Signed-off-by: Li Li <boolli@...gle.com>
> > ---
> >  drivers/net/ethernet/intel/idpf/idpf_lib.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/intel/idpf/idpf_lib.c b/drivers/net/ethernet/intel/idpf/idpf_lib.c
> > index 131a8121839bd..7af4214ec44de 100644
> > --- a/drivers/net/ethernet/intel/idpf/idpf_lib.c
> > +++ b/drivers/net/ethernet/intel/idpf/idpf_lib.c
> > @@ -1308,8 +1308,10 @@ static struct idpf_vport *idpf_vport_alloc(struct idpf_adapter *adapter,
> >
> >  free_rss_key:
> >         kfree(rss_data->rss_key);
> > +       rss_data->rss_key = NULL;
> >  free_vector_idxs:
> >         kfree(vport->q_vector_idxs);
> > +       vport->q_vector_idxs = NULL;
>
> vport is freed right after this line.
>
> vport->q_vector_idxs content is not relevant.
>
> If anything tries to deref vport->any_field ater at this point, there
> is another bug. KASAN might help.

Thank you Eric! I realized this after this patch and have sent out a
v2 patch with this line removed as well.

>
> >  free_vport:
> >         kfree(vport);
> >
> > --
> > 2.52.0.457.g6b5491de43-goog
> >