Subject: Re: [PATCH net v2 1/1] mlxbf_gige: Fix kernel panic at shutdown

From: Leon Romanovsky <[email-masked]>
Date: Mon, 12 Jun 2023 14:59:25 +0300

On Mon, Jun 12, 2023 at 01:34:49PM +0200, Maciej Fijalkowski wrote:
> On Sun, Jun 11, 2023 at 09:11:25PM +0300, Leon Romanovsky wrote:
> > On Wed, Jun 07, 2023 at 10:03:35AM -0400, Asmaa Mnebhi wrote:
> > > There is a race condition happening during shutdown due to pending napi transactions.
> > > Since mlxbf_gige_poll is still running, it tries to access a NULL pointer and as a
> > > result causes a kernel panic.
> > > To fix this during shutdown, invoke mlxbf_gige_remove to disable and dequeue napi.
> > > 
> > > Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
> > > Signed-off-by: Asmaa Mnebhi <[email-masked]>
> > > ---
> > >  .../net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c    | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> > > index 694de9513b9f..609d038b034e 100644
> > > --- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> > > +++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> > > @@ -475,6 +475,9 @@ static int mlxbf_gige_remove(struct platform_device *pdev)
> > >  {
> > >  	struct mlxbf_gige *priv = platform_get_drvdata(pdev);
> > >  
> > > +	if (!priv)
> > > +		return 0;
> > > +
> > 
> > How can this check be correct? You are removing mlxbf_gige driver, priv
> > should be always exist here.
> 
> Asmaa please include v1->v2 diff next time.
> 
> Leon, look at v1 discussion:
> https://lore.kernel.org/netdev/[email-masked]/

Thanks for the link.

As far as I can tell, the calls to .shutdown() and .remove() are
mutually exclusive. It is impossible to go twice and reach scenario
which Paolo mentioned - double call to unregister_netdevice().

Thanks

> 
> > 
> > >  	unregister_netdev(priv->netdev);
> > >  	phy_disconnect(priv->netdev->phydev);
> > >  	mlxbf_gige_mdio_remove(priv);
> > > @@ -485,10 +488,7 @@ static int mlxbf_gige_remove(struct platform_device *pdev)
> > >  
> > >  static void mlxbf_gige_shutdown(struct platform_device *pdev)
> > >  {
> > > -	struct mlxbf_gige *priv = platform_get_drvdata(pdev);
> > > -
> > > -	writeq(0, priv->base + MLXBF_GIGE_INT_EN);
> > > -	mlxbf_gige_clean_port(priv);
> > > +	mlxbf_gige_remove(pdev);
> > >  }
> > >  
> > >  static const struct acpi_device_id __maybe_unused mlxbf_gige_acpi_match[] = {
> > > -- 
> > > 2.30.1
> > > 
> > > 
> >