Message-ID: <ZrthebTBERMWN1DR@lzaremba-mobl.ger.corp.intel.com>
Date: Tue, 13 Aug 2024 15:36:57 +0200
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, "David S. Miller" <davem@...emloft.net>, "Jacob
 Keller" <jacob.e.keller@...el.com>, Eric Dumazet <edumazet@...gle.com>,
	"Jakub Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	"Jesper Dangaard Brouer" <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
	<magnus.karlsson@...el.com>, Michal Kubiak <michal.kubiak@...el.com>,
	Wojciech Drewek <wojciech.drewek@...el.com>, Amritha Nambiar
	<amritha.nambiar@...el.com>
Subject: Re: [PATCH iwl-net v2 2/6] ice: protect XDP configuration with a
 mutex

On Tue, Aug 13, 2024 at 01:31:57PM +0200, Maciej Fijalkowski wrote:
> On Wed, Jul 24, 2024 at 06:48:33PM +0200, Larysa Zaremba wrote:
> > The main threat to data consistency in ice_xdp() is a possible asynchronous
> > PF reset. It can be triggered by a user or by TX timeout handler.
> > 
> > XDP setup and PF reset code access the same resources in the following
> > sections:
> > * ice_vsi_close() in ice_prepare_for_reset() - already rtnl-locked
> > * ice_vsi_rebuild() for the PF VSI - not protected
> > * ice_vsi_open() - already rtnl-locked
> > 
> > With an unfortunate timing, such accesses can result in a crash such as the
> > one below:
> > 
> > [ +1.999878] ice 0000:b1:00.0: Registered XDP mem model MEM_TYPE_XSK_BUFF_POOL on Rx ring 14
> > [ +2.002992] ice 0000:b1:00.0: Registered XDP mem model MEM_TYPE_XSK_BUFF_POOL on Rx ring 18
> > [Mar15 18:17] ice 0000:b1:00.0 ens801f0np0: NETDEV WATCHDOG: CPU: 38: transmit queue 14 timed out 80692736 ms
> > [ +0.000093] ice 0000:b1:00.0 ens801f0np0: tx_timeout: VSI_num: 6, Q 14, NTC: 0x0, HW_HEAD: 0x0, NTU: 0x0, INT: 0x4000001
> > [ +0.000012] ice 0000:b1:00.0 ens801f0np0: tx_timeout recovery level 1, txqueue 14
> > [ +0.394718] ice 0000:b1:00.0: PTP reset successful
> > [ +0.006184] BUG: kernel NULL pointer dereference, address: 0000000000000098
> > [ +0.000045] #PF: supervisor read access in kernel mode
> > [ +0.000023] #PF: error_code(0x0000) - not-present page
> > [ +0.000023] PGD 0 P4D 0
> > [ +0.000018] Oops: 0000 [#1] PREEMPT SMP NOPTI
> > [ +0.000023] CPU: 38 PID: 7540 Comm: kworker/38:1 Not tainted 6.8.0-rc7 #1
> > [ +0.000031] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0014.082620210524 08/26/2021
> > [ +0.000036] Workqueue: ice ice_service_task [ice]
> > [ +0.000183] RIP: 0010:ice_clean_tx_ring+0xa/0xd0 [ice]
> > [...]
> > [ +0.000013] Call Trace:
> > [ +0.000016] <TASK>
> > [ +0.000014] ? __die+0x1f/0x70
> > [ +0.000029] ? page_fault_oops+0x171/0x4f0
> > [ +0.000029] ? schedule+0x3b/0xd0
> > [ +0.000027] ? exc_page_fault+0x7b/0x180
> > [ +0.000022] ? asm_exc_page_fault+0x22/0x30
> > [ +0.000031] ? ice_clean_tx_ring+0xa/0xd0 [ice]
> > [ +0.000194] ice_free_tx_ring+0xe/0x60 [ice]
> > [ +0.000186] ice_destroy_xdp_rings+0x157/0x310 [ice]
> > [ +0.000151] ice_vsi_decfg+0x53/0xe0 [ice]
> > [ +0.000180] ice_vsi_rebuild+0x239/0x540 [ice]
> > [ +0.000186] ice_vsi_rebuild_by_type+0x76/0x180 [ice]
> > [ +0.000145] ice_rebuild+0x18c/0x840 [ice]
> > [ +0.000145] ? delay_tsc+0x4a/0xc0
> > [ +0.000022] ? delay_tsc+0x92/0xc0
> > [ +0.000020] ice_do_reset+0x140/0x180 [ice]
> > [ +0.000886] ice_service_task+0x404/0x1030 [ice]
> > [ +0.000824] process_one_work+0x171/0x340
> > [ +0.000685] worker_thread+0x277/0x3a0
> > [ +0.000675] ? preempt_count_add+0x6a/0xa0
> > [ +0.000677] ? _raw_spin_lock_irqsave+0x23/0x50
> > [ +0.000679] ? __pfx_worker_thread+0x10/0x10
> > [ +0.000653] kthread+0xf0/0x120
> > [ +0.000635] ? __pfx_kthread+0x10/0x10
> > [ +0.000616] ret_from_fork+0x2d/0x50
> > [ +0.000612] ? __pfx_kthread+0x10/0x10
> > [ +0.000604] ret_from_fork_asm+0x1b/0x30
> > [ +0.000604] </TASK>
> > 
> > The previous way of handling this through returning -EBUSY is not viable,
> > particularly when destroying AF_XDP socket, because the kernel proceeds
> > with removal anyway.
> > 
> > There is plenty of code between those calls and there is no need to create
> > a large critical section that covers all of them, same as there is no need
> > to protect ice_vsi_rebuild() with rtnl_lock().
> > 
> > Add xdp_state_lock mutex to protect ice_vsi_rebuild() and ice_xdp().
> > 
> > Leaving unprotected sections in between would result in two states that
> > have to be considered:
> > 1. when the VSI is closed, but not yet rebuild
> > 2. when VSI is already rebuild, but not yet open
> > 
> > The latter case is actually already handled through !netif_running() case,
> > we just need to adjust flag checking a little. The former one is not as
> > trivial, because between ice_vsi_close() and ice_vsi_rebuild(), a lot of
> > hardware interaction happens, this can make adding/deleting rings exit
> > with an error. Luckily, VSI rebuild is pending and can apply new
> > configuration for us in a managed fashion.
> > 
> > Therefore, add an additional VSI state flag ICE_VSI_REBUILD_PENDING to
> > indicate that ice_xdp() can just hot-swap the program.
> 
> couldn't this be a separate patch?
> 

I think, this is an integral part of the synchronization concept, without it 
locking the rebuild would not have much sense.

> > 
> > Fixes: 2d4238f55697 ("ice: Add support for AF_XDP")
> > Fixes: efc2214b6047 ("ice: Add support for XDP")
> > Reviewed-by: Wojciech Drewek <wojciech.drewek@...el.com>
> > Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
> > ---
> >  drivers/net/ethernet/intel/ice/ice.h      |  2 ++
> >  drivers/net/ethernet/intel/ice/ice_lib.c  | 26 +++++++++++++++--------
> >  drivers/net/ethernet/intel/ice/ice_main.c | 19 ++++++++++++-----
> >  drivers/net/ethernet/intel/ice/ice_xsk.c  |  3 ++-
> >  4 files changed, 35 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
> > index 99a75a59078e..3d7a0abc13ab 100644
> > --- a/drivers/net/ethernet/intel/ice/ice.h
> > +++ b/drivers/net/ethernet/intel/ice/ice.h
> > @@ -318,6 +318,7 @@ enum ice_vsi_state {
> >  	ICE_VSI_UMAC_FLTR_CHANGED,
> >  	ICE_VSI_MMAC_FLTR_CHANGED,
> >  	ICE_VSI_PROMISC_CHANGED,
> > +	ICE_VSI_REBUILD_PENDING,
> >  	ICE_VSI_STATE_NBITS		/* must be last */
> >  };
> >  
> > @@ -411,6 +412,7 @@ struct ice_vsi {
> >  	struct ice_tx_ring **xdp_rings;	 /* XDP ring array */
> >  	u16 num_xdp_txq;		 /* Used XDP queues */
> >  	u8 xdp_mapping_mode;		 /* ICE_MAP_MODE_[CONTIG|SCATTER] */
> > +	struct mutex xdp_state_lock;
> >  
> >  	struct net_device **target_netdevs;
> >  
> > diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> > index 5f2ddcaf7031..bbef5ec67cae 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> > @@ -447,6 +447,7 @@ static void ice_vsi_free(struct ice_vsi *vsi)
> >  
> >  	ice_vsi_free_stats(vsi);
> >  	ice_vsi_free_arrays(vsi);
> > +	mutex_destroy(&vsi->xdp_state_lock);
> >  	mutex_unlock(&pf->sw_mutex);
> >  	devm_kfree(dev, vsi);
> >  }
> > @@ -626,6 +627,8 @@ static struct ice_vsi *ice_vsi_alloc(struct ice_pf *pf)
> >  	pf->next_vsi = ice_get_free_slot(pf->vsi, pf->num_alloc_vsi,
> >  					 pf->next_vsi);
> >  
> > +	mutex_init(&vsi->xdp_state_lock);
> > +
> >  unlock_pf:
> >  	mutex_unlock(&pf->sw_mutex);
> >  	return vsi;
> > @@ -2973,19 +2976,24 @@ int ice_vsi_rebuild(struct ice_vsi *vsi, u32 vsi_flags)
> >  	if (WARN_ON(vsi->type == ICE_VSI_VF && !vsi->vf))
> >  		return -EINVAL;
> >  
> > +	mutex_lock(&vsi->xdp_state_lock);
> > +	clear_bit(ICE_VSI_REBUILD_PENDING, vsi->state);
> > +
> >  	ret = ice_vsi_realloc_stat_arrays(vsi);
> >  	if (ret)
> > -		goto err_vsi_cfg;
> > +		goto unlock;
> >  
> >  	ice_vsi_decfg(vsi);
> >  	ret = ice_vsi_cfg_def(vsi);
> >  	if (ret)
> > -		goto err_vsi_cfg;
> > +		goto unlock;
> >  
> >  	coalesce = kcalloc(vsi->num_q_vectors,
> >  			   sizeof(struct ice_coalesce_stored), GFP_KERNEL);
> > -	if (!coalesce)
> > -		return -ENOMEM;
> > +	if (!coalesce) {
> > +		ret = -ENOMEM;
> 
> Knee-jerk reaction would be to deconfig things that ice_vsi_cfg_def()
> setup above.
> 
> So I think the order of kfree and ice_vsi_decfg should be swapped,
> something like:
> 
> 	if (!coalesce) {
> 		ret = -ENOMEM;
> 		goto err_mem_alloc;
> 	}
> 
> err_vsi_cfg_tc_lan:
> 	kfree(coalesce);
> err_mem_alloc:
> 	ice_vsi_decfg(vsi);
> unlock:
> 	mutex_unlock(&vsi->xdp_state_lock);
> 	return ret;
> 
> 
> or am I missing something?
> 

You are correct, v3 it is :D

> > +		goto unlock;
> > +	}
> >  
> >  	prev_num_q_vectors = ice_vsi_rebuild_get_coalesce(vsi, coalesce);
> >  
> > @@ -2996,19 +3004,19 @@ int ice_vsi_rebuild(struct ice_vsi *vsi, u32 vsi_flags)
> >  			goto err_vsi_cfg_tc_lan;
> >  		}
> >  
> > -		kfree(coalesce);
> > -		return ice_schedule_reset(pf, ICE_RESET_PFR);
> > +		ret = ice_schedule_reset(pf, ICE_RESET_PFR);
> > +		goto err_vsi_cfg_tc_lan;
> >  	}
> >  
> >  	ice_vsi_rebuild_set_coalesce(vsi, coalesce, prev_num_q_vectors);
> >  	kfree(coalesce);
> > -
> > -	return 0;
> > +	goto unlock;
> >  
> >  err_vsi_cfg_tc_lan:
> >  	ice_vsi_decfg(vsi);
> >  	kfree(coalesce);
> > -err_vsi_cfg:
> > +unlock:
> > +	mutex_unlock(&vsi->xdp_state_lock);
> >  	return ret;
> >  }
> >  
> > diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
> > index 8ed1798bb06e..e50526b491fc 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_main.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_main.c
> > @@ -611,6 +611,7 @@ ice_prepare_for_reset(struct ice_pf *pf, enum ice_reset_req reset_type)
> >  	/* clear SW filtering DB */
> >  	ice_clear_hw_tbls(hw);
> >  	/* disable the VSIs and their queues that are not already DOWN */
> > +	set_bit(ICE_VSI_REBUILD_PENDING, ice_get_main_vsi(pf)->state);
> >  	ice_pf_dis_all_vsi(pf, false);
> >  
> >  	if (test_bit(ICE_FLAG_PTP_SUPPORTED, pf->flags))
> > @@ -3011,7 +3012,8 @@ ice_xdp_setup_prog(struct ice_vsi *vsi, struct bpf_prog *prog,
> >  	}
> >  
> >  	/* hot swap progs and avoid toggling link */
> > -	if (ice_is_xdp_ena_vsi(vsi) == !!prog) {
> > +	if (ice_is_xdp_ena_vsi(vsi) == !!prog ||
> > +	    test_bit(ICE_VSI_REBUILD_PENDING, vsi->state)) {
> >  		ice_vsi_assign_bpf_prog(vsi, prog);
> >  		return 0;
> >  	}
> > @@ -3083,21 +3085,28 @@ static int ice_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> >  {
> >  	struct ice_netdev_priv *np = netdev_priv(dev);
> >  	struct ice_vsi *vsi = np->vsi;
> > +	int ret;
> >  
> >  	if (vsi->type != ICE_VSI_PF) {
> >  		NL_SET_ERR_MSG_MOD(xdp->extack, "XDP can be loaded only on PF VSI");
> >  		return -EINVAL;
> >  	}
> >  
> > +	mutex_lock(&vsi->xdp_state_lock);
> > +
> >  	switch (xdp->command) {
> >  	case XDP_SETUP_PROG:
> > -		return ice_xdp_setup_prog(vsi, xdp->prog, xdp->extack);
> > +		ret = ice_xdp_setup_prog(vsi, xdp->prog, xdp->extack);
> > +		break;
> >  	case XDP_SETUP_XSK_POOL:
> > -		return ice_xsk_pool_setup(vsi, xdp->xsk.pool,
> > -					  xdp->xsk.queue_id);
> > +		ret = ice_xsk_pool_setup(vsi, xdp->xsk.pool, xdp->xsk.queue_id);
> > +		break;
> >  	default:
> > -		return -EINVAL;
> > +		ret = -EINVAL;
> >  	}
> > +
> > +	mutex_unlock(&vsi->xdp_state_lock);
> > +	return ret;
> >  }
> >  
> >  /**
> > diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > index a65955eb23c0..2c1a843ba200 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > @@ -379,7 +379,8 @@ int ice_xsk_pool_setup(struct ice_vsi *vsi, struct xsk_buff_pool *pool, u16 qid)
> >  		goto failure;
> >  	}
> >  
> > -	if_running = netif_running(vsi->netdev) && ice_is_xdp_ena_vsi(vsi);
> > +	if_running = !test_bit(ICE_VSI_DOWN, vsi->state) &&
> > +		     ice_is_xdp_ena_vsi(vsi);
> >  
> >  	if (if_running) {
> >  		struct ice_rx_ring *rx_ring = vsi->rx_rings[qid];
> > -- 
> > 2.43.0
> > 

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