[PATCH v1] i40e: Lock VF cloud filter list operations

[Binbin Deng <18983559317@163.com>]

A VF's cloud-filter hlist is modified by the virtchnl add and delete
handlers and by i40e_del_all_cloud_filters(), which runs when ADq is
disabled or when the VF loses trusted status.  These paths do not share a
lock.  In particular, the PF's async VF-message handler can process
VIRTCHNL_OP_DEL_CLOUD_FILTER while host-side ndo_set_vf_trust() removes
every cloud filter for that VF.

The race is reachable from a guest by issuing cloud-filter virtchnl
requests while the host revokes VF trust or disables ADq.  The VF-message
handler can traverse nodes that the bulk-delete path has already freed, or
both paths can remove the same node.  The result can be a KASAN
use-after-free, hlist corruption, incorrect filter accounting, or a panic.
The virtchnl operation-pending bit does not serialize this host-side trust
path.

Serialize cloud-filter control operations with a mutex.  Hold it across
the firmware add or delete, hlist update, and free, so bulk deletion and
individual add/delete operations cannot observe a partially removed list.
The lock is file-local and slow-path only.

Found during a static-analysis-assisted audit: candidate sites were
surfaced by a Coccinelle rule, and the reader/writer paths were
confirmed by LLM-assisted (GLM-5.3) code inspection. Due to a lack 
of hardware infrastructureThe issue was not observed at runtime.
It is identified by code inspection only.

Fixes: e284fc280473 ("i40e: Add and delete cloud filter")
Assisted-by: GLM-5.3 coccinelle
Signed-off-by: Binbin Deng <18983559317@163.com>
---
 drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
index a26c3d47ec15..f73a710f42f1 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
@@ -3740,6 +3740,8 @@ static struct i40e_vsi *i40e_find_vsi_from_seid(struct i40e_vf *vf, u16 seid)
  *
  * This function deletes all cloud filters
  **/
+static DEFINE_MUTEX(i40e_vf_cloud_filter_lock);
+
 static void i40e_del_all_cloud_filters(struct i40e_vf *vf)
 {
 	struct i40e_cloud_filter *cfilter = NULL;
@@ -3748,6 +3750,7 @@ static void i40e_del_all_cloud_filters(struct i40e_vf *vf)
 	struct hlist_node *node;
 	int ret;
 
+	mutex_lock(&i40e_vf_cloud_filter_lock);
 	hlist_for_each_entry_safe(cfilter, node,
 				  &vf->cloud_filter_list, cloud_node) {
 		vsi = i40e_find_vsi_from_seid(vf, cfilter->seid);
@@ -3773,6 +3776,7 @@ static void i40e_del_all_cloud_filters(struct i40e_vf *vf)
 		kfree(cfilter);
 		vf->num_cloud_filters--;
 	}
+	mutex_unlock(&i40e_vf_cloud_filter_lock);
 }
 
 /**
@@ -3856,6 +3860,7 @@ static int i40e_vc_del_cloud_filter(struct i40e_vf *vf, u8 *msg)
 	}
 
 	/* get the vsi to which the tc belongs to */
+	mutex_lock(&i40e_vf_cloud_filter_lock);
 	vsi = pf->vsi[vf->ch[vcf->action_meta].vsi_idx];
 	cfilter.seid = vsi->seid;
 	cfilter.flags = vcf->field_flags;
@@ -3870,6 +3875,7 @@ static int i40e_vc_del_cloud_filter(struct i40e_vf *vf, u8 *msg)
 			"VF %d: Failed to delete cloud filter, err %pe aq_err %s\n",
 			vf->vf_id, ERR_PTR(ret),
 			libie_aq_str(pf->hw.aq.asq_last_status));
+		mutex_unlock(&i40e_vf_cloud_filter_lock);
 		goto err;
 	}
 
@@ -3901,6 +3907,7 @@ static int i40e_vc_del_cloud_filter(struct i40e_vf *vf, u8 *msg)
 		kfree(cf);
 		vf->num_cloud_filters--;
 	}
+	mutex_unlock(&i40e_vf_cloud_filter_lock);
 
 err:
 	return i40e_vc_send_resp_to_vf(vf, VIRTCHNL_OP_DEL_CLOUD_FILTER,
@@ -4002,6 +4009,7 @@ static int i40e_vc_add_cloud_filter(struct i40e_vf *vf, u8 *msg)
 	}
 
 	/* get the VSI to which the TC belongs to */
+	mutex_lock(&i40e_vf_cloud_filter_lock);
 	vsi = pf->vsi[vf->ch[vcf->action_meta].vsi_idx];
 	cfilter->seid = vsi->seid;
 	cfilter->flags = vcf->field_flags;
@@ -4016,6 +4024,7 @@ static int i40e_vc_add_cloud_filter(struct i40e_vf *vf, u8 *msg)
 			"VF %d: Failed to add cloud filter, err %pe aq_err %s\n",
 			vf->vf_id, ERR_PTR(aq_ret),
 			libie_aq_str(pf->hw.aq.asq_last_status));
+		mutex_unlock(&i40e_vf_cloud_filter_lock);
 		goto err_free;
 	}
 
@@ -4024,6 +4033,7 @@ static int i40e_vc_add_cloud_filter(struct i40e_vf *vf, u8 *msg)
 	/* release the pointer passing it to the collection */
 	cfilter = NULL;
 	vf->num_cloud_filters++;
+	mutex_unlock(&i40e_vf_cloud_filter_lock);
 err_free:
 	kfree(cfilter);
 err_out:
-- 
2.43.0