Re: [PATCH net 5/7] net/mlx5e: macsec: Delete remaining SecYs during cleanup

[Cosmin Ratiu <cratiu@nvidia.com>]

On Mon, 2026-09-21 at 18:49 +0000, netdev-bot+sashiko@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential
> issue(s) to consider.
> 
> Critical: 0 · High: 2 (1) · Medium: 0 (1) · Low: 0
> 
> If you believe none of the issues are legitimate, please reply to
> each
> issue of Medium severity or higher and explain why the AI is wrong.
> If any of them are legitimate and you plan to respin, please let
> patchwork
> know by including "pw-bot: cr" as a separate line at the end of your
> reply
> (one such reply per series is enough).
> 
> - [High] mlx5e_macsec_cleanup() frees the MACsec context and sets
>   `priv->macsec = NULL` (macsec.c:1826-1827) without ever
> withdrawing…
> - [High] mlx5e_macsec_cleanup() takes macsec->lock only for the new
> SecY-
>   deletion sweep (macsec.c:1814-1819), then drops it and
> destroys/frees…
> 
> Pre-existing issues:
> - [High] macsec_del_rxsc_ctx() (macsec.c:820-849), which this patch
> newly
>   invokes from the bulk cleanup path, releases the RX-SC's xarray…
> - [Medium] Suspend-time cleanup now deletes every programmed SecY,
> SA,
>   encryption key, MACsec HW object and steering rule…
> 
> --
> 
> net/mlx5e: macsec: Delete remaining SecYs during cleanup
> 
> The patch factors the SecY teardown out of mlx5e_macsec_del_secy()
> into a
> new macsec_del_secy() helper, and calls it for every remaining entry
> of
> macsec->macsec_device_list_head from mlx5e_macsec_cleanup().  It also
> adds xa_destroy(), clears mdev->macsec_fs and clears priv->macsec at
> the
> end of cleanup.
> 
> A few questions below about the teardown ordering and about the
> callbacks
> that remain registered after cleanup has run.
> 
> > diff --git
> > a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
> > b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
> > index 20eec345b36cd..84ce388d3846e 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
> 
> [ ... ]
> 
> > @@ -1272,7 +1260,7 @@ static int mlx5e_macsec_del_secy(struct
> > macsec_context *ctx)
> >  
> >  	list = &macsec_device->macsec_rx_sc_list_head;
> >  	list_for_each_entry_safe(rx_sc, tmp, list,
> > rx_sc_list_element)
> > -		macsec_del_rxsc_ctx(macsec, rx_sc, ctx->secy-
> > >netdev);
> > +		macsec_del_rxsc_ctx(macsec, rx_sc, netdev);
> 
> [Severity: High]
> 
> This isn't a bug introduced by this patch, but since the cleanup
> sweep is
> now a second caller of macsec_del_rxsc_ctx() it seems worth asking
> about
> the lifetime of rx_sc->sc_xarray_element there:
> 
> drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c:macsec_del_
> rxsc_ctx() {
> 	...
> 	list_del_rcu(&rx_sc->rx_sc_list_element);
> 	xa_erase(&macsec->sc_xarray, rx_sc->sc_xarray_element-
> >fs_id);
> 	dst_release(&rx_sc->md_dst->dst);
> 	kfree(rx_sc->sc_xarray_element);
> 	kfree_rcu_mightsleep(rx_sc);
> }
> 
> The RX datapath loads that element under RCU:
> 
> drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c:mlx5e_macse
> c_offload_handle_rx_skb() {
> 	...
> 	rcu_read_lock();
> 	sc_xarray_element = xa_load(&macsec->sc_xarray, fs_id);
> 	rx_sc = sc_xarray_element ? sc_xarray_element->rx_sc : NULL;
> 	if (rx_sc && rx_sc->md_dst) {
> 	...
> }
> 
> Only rx_sc is freed via kfree_rcu_mightsleep(); sc_xarray_element is
> freed
> with plain kfree() right after xa_erase().  Can a reader that already
> obtained sc_xarray_element from xa_load() then dereference freed
> memory for
> sc_xarray_element->rx_sc, and go on to dereference the resulting
> garbage
> pointer at rx_sc->md_dst?
> 
> The comment just above those lines says:
> 
> 	/* At this point the relevant MACsec offload Rx rule already
> removed at
> 	 * mlx5e_macsec_cleanup_sa need to wait for datapath to
> finish current
> 	 * Rx related data propagating using xa_erase which uses rcu
> to sync,
> 	 * once fs_id is erased then this rx_sc is hidden from
> datapath.
> 	 */
> 
> xa_erase() stores NULL into the slot but does not wait for a grace
> period,
> so is the stated justification for the immediate kfree() of
> sc_xarray_element accurate?

Will fix.

> 
> >  
> >  	kfree(macsec_device->dev_addr);
> >  	macsec_device->dev_addr = NULL;
> > @@ -1280,7 +1268,24 @@ static int mlx5e_macsec_del_secy(struct
> > macsec_context *ctx)
> >  	list_del_rcu(&macsec_device->macsec_device_list_element);
> >  	--macsec->num_of_devices;
> >  	kfree(macsec_device);
> > +}
> > +
> > +static int mlx5e_macsec_del_secy(struct macsec_context *ctx)
> > +{
> > +	struct mlx5e_priv *priv = macsec_netdev_priv(ctx->netdev);
> > +	struct mlx5e_macsec *macsec = priv->macsec;
> > +	struct mlx5e_macsec_device *macsec_device;
> > +	int err = 0;
> >  
> > +	mutex_lock(&macsec->lock);
> > +	macsec_device =
> > mlx5e_macsec_get_macsec_device_context(macsec, ctx);
> > +	if (!macsec_device) {
> > +		netdev_err(ctx->netdev, "MACsec offload: Failed to
> > find device context\n");
> > +		err = -EINVAL;
> > +		goto out;
> > +	}
> > +
> > +	macsec_del_secy(macsec, macsec_device);
> >  out:
> >  	mutex_unlock(&macsec->lock);
> >  
> > @@ -1796,6 +1801,7 @@ int mlx5e_macsec_init(struct mlx5e_priv
> > *priv)
> >  
> >  void mlx5e_macsec_cleanup(struct mlx5e_priv *priv)
> >  {
> > +	struct mlx5e_macsec_device *macsec_device, *tmp;
> >  	struct mlx5e_macsec *macsec = priv->macsec;
> >  	struct mlx5_core_dev *mdev = priv->mdev;
> >  
> > @@ -1803,9 +1809,20 @@ void mlx5e_macsec_cleanup(struct mlx5e_priv
> > *priv)
> >  		return;
> >  
> >  	mlx5_notifier_unregister(mdev, &macsec->nb);
> > -	mlx5_macsec_fs_cleanup(mdev->macsec_fs);
> >  	destroy_workqueue(macsec->wq);
> > +
> > +	mutex_lock(&macsec->lock);
> > +	list_for_each_entry_safe(macsec_device, tmp,
> > +				 &macsec->macsec_device_list_head,
> > +				 macsec_device_list_element)
> > +		macsec_del_secy(macsec, macsec_device);
> > +	mutex_unlock(&macsec->lock);
> 
> [Severity: Medium]
> 
> This is a pre-existing restoration gap rather than something this
> patch
> introduces, and the commit message already says fixing it is out of
> scope,
> but it may be worth spelling out what the observable result is.
> 
> After this sweep plus mlx5_macsec_fs_cleanup(), every SecY, SA,
> encryption
> key, MACsec object and steering rule is gone, while the MACsec upper
> netdevices stay registered with their SecYs still marked offloaded.
> mlx5e_macsec_init() on resume only allocates a fresh context, an
> empty
> sc_xarray, a new ASO and a new flow-steering instance, with no
> replay.
> 
> So on resume, does offloaded TX end up dropping frames here?
> 
> drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c:mlx5e_macse
> c_handle_tx_skb() {
> 	...
> 	fs_id = mlx5_macsec_fs_get_fs_id_from_hashtable(macsec-
> >mdev->macsec_fs,
> 							&md_dst-
> >u.macsec_info.sci);
> 	if (!fs_id)
> 		goto err_out;
> 	...
> }
> 
> and do later control operations on those retained SecYs fail with -
> EINVAL
> from the device-context lookup in mlx5e_macsec_del_secy(), which also
> makes
> macsec_update_offload() abort the transition?

Will improve.

> 
> > +
> > +	xa_destroy(&macsec->sc_xarray);
> > +	mlx5_macsec_fs_cleanup(mdev->macsec_fs);
> > +	mdev->macsec_fs = NULL;
> >  	mlx5e_macsec_aso_cleanup(&macsec->aso, mdev);
> >  	mutex_destroy(&macsec->lock);
> >  	kfree(macsec);
> 
> [Severity: High]
> 
> macsec->lock is released before mutex_destroy() and kfree(macsec),
> and
> priv->macsec is cleared only after the free.  Every offload callback
> reads
> priv->macsec locklessly and then blocks on that same mutex, for
> example
> mlx5e_macsec_add_secy() and the rewritten mlx5e_macsec_del_secy():
> 
> 	struct mlx5e_macsec *macsec = priv->macsec;
> 	...
> 	mutex_lock(&macsec->lock);
> 
> mlx5e_macsec_cleanup() runs from mlx5e_nic_disable() after
> rtnl_unlock(),
> while the MACsec core dispatches the mdo_* ops under rtnl
> (macsec_newlink()
> -> mdo_add_secy, macsec_upd_offload() -> macsec_update_offload()), so
> rtnl
> does not serialize the two paths and macsec->lock is the only mutual
> exclusion:
> 
> CPU0 (netlink, rtnl held)
> mlx5e_macsec_add_secy()
> 	macsec = priv->macsec;		/* still non-NULL */
> 	mutex_lock(&macsec->lock);	/* blocks */
> 
> CPU1 (devlink reload / health recovery / suspend, no rtnl)
> mlx5e_macsec_cleanup()
> 	mutex_unlock(&macsec->lock);
> 	...
> 	mutex_destroy(&macsec->lock);
> 	kfree(macsec);
> 	priv->macsec = NULL;
> 
> Can CPU0 then acquire a mutex inside freed memory, list_add a new
> macsec_device into the freed macsec_device_list_head, and
> mutex_unlock()
> freed memory?  A SecY added in that window would also be leaked,
> which is
> the case this patch is trying to close.  Would clearing the gating
> state
> (and withdrawing the offload registration) before dropping the lock
> and
> freeing be a better ordering?
> 
> > +	priv->macsec = NULL;
> >  }

Will fix.

> 
> [Severity: High]
> 
> Clearing priv->macsec here leaves the offload registration in place.
> netdev->macsec_ops and NETIF_F_HW_MACSEC are set once in
> mlx5e_macsec_build_netdev(), called from mlx5e_build_nic_netdev() at
> netdev
> creation, and nothing in mlx5e_macsec_cleanup() reverses that.  The
> core
> only checks those two fields:
> 
> drivers/net/macsec.c:macsec_check_offload() {
> 	...
> 		return macsec->real_dev->features &
> NETIF_F_HW_MACSEC &&
> 		       macsec->real_dev->macsec_ops;
> 	...
> }
> 
> There is no netif_device_present() test there, and none of the mlx5e
> callbacks NULL-check priv->macsec; they all start with
> mutex_lock(&priv->macsec->lock), and the rewritten
> mlx5e_macsec_del_secy()
> does:
> 
> 	struct mlx5e_macsec *macsec = priv->macsec;
> 	...
> 	mutex_lock(&macsec->lock);
> 
> Since mlx5e_macsec_cleanup() is called from mlx5e_nic_disable() after
> rtnl_unlock() and with the netdev still registered (only
> netif_device_detach()'ed), can "ip link del macsec0" reach
> macsec_common_dellink() -> mdo_del_secy -> mlx5e_macsec_del_secy()
> with
> priv->macsec == NULL and oops on the mutex_lock()?
> 
> The same applies indefinitely if mlx5e_macsec_init() fails on resume,
> since
> mlx5e_nic_enable() only logs the error:
> 
> drivers/net/ethernet/mellanox/mlx5/core/en_main.c:mlx5e_nic_enable()
> {
> 	...
> 	err = mlx5e_macsec_init(priv);
> 	if (err)
> 		mlx5_core_err(mdev, "MACsec initialization failed,
> %d\n", err);
> 	...
> }
> 
> so priv->macsec stays NULL while the ops remain advertised.  The TX
> helpers
> reached from en_accel.h have the same exposure, for instance
> mlx5e_macsec_handle_tx_skb() dereferencing macsec->mdev->macsec_fs
> with no
> NULL check on macsec.  Should cleanup also drop macsec_ops and
> NETIF_F_HW_MACSEC, or should the callbacks check priv->macsec?
> 

Will fix by having the driver ops check for priv->macsec before doing
anything.

Cosmin.