ice: protect XDP configuration with a mutex

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.

Also, as ice_vsi_rebuild() flow is touched in this patch, make it more
consistent by deconfiguring VSI when coalesce allocation fails.

Fixes: 2d4238f ("ice: Add support for AF_XDP")
Fixes: efc2214 ("ice: Add support for XDP")
Reviewed-by: Wojciech Drewek <[email protected]>
Reviewed-by: Jacob Keller <[email protected]>
Tested-by: Chandan Kumar Rout <[email protected]>
Signed-off-by: Larysa Zaremba <[email protected]>
Reviewed-by: Maciej Fijalkowski <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>

Author: walking-machine

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;
 

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;
@@ -2972,42 +2975,47 @@ 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);
+
 	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;
+		goto decfg;
+	}
 
 	prev_num_q_vectors = ice_vsi_rebuild_get_coalesce(vsi, coalesce);
 
 	ret = ice_vsi_cfg_tc_lan(pf, vsi);
 	if (ret) {
 		if (vsi_flags & ICE_VSI_FLAG_INIT) {
 			ret = -EIO;
-			goto err_vsi_cfg_tc_lan;
+			goto free_coalesce;
 		}
 
-		kfree(coalesce);
-		return ice_schedule_reset(pf, ICE_RESET_PFR);
+		ret = ice_schedule_reset(pf, ICE_RESET_PFR);
+		goto free_coalesce;
 	}
 
 	ice_vsi_rebuild_set_coalesce(vsi, coalesce, prev_num_q_vectors);
-	kfree(coalesce);
+	clear_bit(ICE_VSI_REBUILD_PENDING, vsi->state);
 
-	return 0;
-
-err_vsi_cfg_tc_lan:
-	ice_vsi_decfg(vsi);
+free_coalesce:
 	kfree(coalesce);
-err_vsi_cfg:
+decfg:
+	if (ret)
+		ice_vsi_decfg(vsi);
+unlock:
+	mutex_unlock(&vsi->xdp_state_lock);
 	return ret;
 }
 

drivers/net/ethernet/intel/ice/ice_main.c

@@ -616,6 +616,7 @@ 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))
@@ -3016,7 +3017,8 @@ 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;
 	}
@@ -3088,21 +3090,28 @@ 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;
 }
 
 /**

drivers/net/ethernet/intel/ice/ice_xsk.c

@@ -390,7 +390,8 @@ 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];