Forwarded: Test for 5a66db916cdde0dbcc1c

[syzbot <syzbot+5a66db916cdde0dbcc1c@syzkaller.appspotmail.com>]

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Subject: Test for 5a66db916cdde0dbcc1c
Author: syoshida@redhat.com

#syz test

diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
index 596ab9791e4d..ff6d2bcb2cca 100644
--- a/include/net/flow_offload.h
+++ b/include/net/flow_offload.h
@@ -673,6 +673,8 @@ int flow_block_cb_setup_simple(struct flow_block_offload *f,
 			       flow_setup_cb_t *cb,
 			       void *cb_ident, void *cb_priv, bool ingress_only);
 
+void flow_block_cb_remove_driver(struct flow_block_cb *block_cb);
+
 enum flow_cls_command {
 	FLOW_CLS_REPLACE,
 	FLOW_CLS_DESTROY,
diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
index bc5169482710..137a44af5e1c 100644
--- a/net/core/flow_offload.c
+++ b/net/core/flow_offload.c
@@ -334,6 +334,8 @@ bool flow_block_cb_is_busy(flow_setup_cb_t *cb, void *cb_ident,
 }
 EXPORT_SYMBOL(flow_block_cb_is_busy);
 
+static DEFINE_MUTEX(flow_block_cb_list_lock);
+
 int flow_block_cb_setup_simple(struct flow_block_offload *f,
 			       struct list_head *driver_block_list,
 			       flow_setup_cb_t *cb,
@@ -341,6 +343,7 @@ int flow_block_cb_setup_simple(struct flow_block_offload *f,
 			       bool ingress_only)
 {
 	struct flow_block_cb *block_cb;
+	int err = 0;
 
 	if (ingress_only &&
 	    f->binder_type != FLOW_BLOCK_BINDER_TYPE_CLSACT_INGRESS)
@@ -348,32 +351,52 @@ int flow_block_cb_setup_simple(struct flow_block_offload *f,
 
 	f->driver_block_list = driver_block_list;
 
+	mutex_lock(&flow_block_cb_list_lock);
+
 	switch (f->command) {
 	case FLOW_BLOCK_BIND:
-		if (flow_block_cb_is_busy(cb, cb_ident, driver_block_list))
-			return -EBUSY;
+		if (flow_block_cb_is_busy(cb, cb_ident, driver_block_list)) {
+			err = -EBUSY;
+			break;
+		}
 
 		block_cb = flow_block_cb_alloc(cb, cb_ident, cb_priv, NULL);
-		if (IS_ERR(block_cb))
-			return PTR_ERR(block_cb);
+		if (IS_ERR(block_cb)) {
+			err = PTR_ERR(block_cb);
+			break;
+		}
 
 		flow_block_cb_add(block_cb, f);
 		list_add_tail(&block_cb->driver_list, driver_block_list);
-		return 0;
+		break;
 	case FLOW_BLOCK_UNBIND:
 		block_cb = flow_block_cb_lookup(f->block, cb, cb_ident);
-		if (!block_cb)
-			return -ENOENT;
+		if (!block_cb) {
+			err = -ENOENT;
+			break;
+		}
 
 		flow_block_cb_remove(block_cb, f);
 		list_del(&block_cb->driver_list);
-		return 0;
+		break;
 	default:
-		return -EOPNOTSUPP;
+		err = -EOPNOTSUPP;
+		break;
 	}
+
+	mutex_unlock(&flow_block_cb_list_lock);
+	return err;
 }
 EXPORT_SYMBOL(flow_block_cb_setup_simple);
 
+void flow_block_cb_remove_driver(struct flow_block_cb *block_cb)
+{
+	mutex_lock(&flow_block_cb_list_lock);
+	list_del(&block_cb->driver_list);
+	mutex_unlock(&flow_block_cb_list_lock);
+}
+EXPORT_SYMBOL(flow_block_cb_remove_driver);
+
 static DEFINE_MUTEX(flow_indr_block_lock);
 static LIST_HEAD(flow_block_indr_list);
 static LIST_HEAD(flow_block_indr_dev_list);
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index fd30e205de84..d60838bceafb 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -414,7 +414,7 @@ static void nft_indr_block_cleanup(struct flow_block_cb *block_cb)
 				    basechain, &extack);
 	nft_net = nft_pernet(net);
 	mutex_lock(&nft_net->commit_mutex);
-	list_del(&block_cb->driver_list);
+	flow_block_cb_remove_driver(block_cb);
 	list_move(&block_cb->list, &bo.cb_list);
 	nft_flow_offload_unbind(&bo, basechain);
 	mutex_unlock(&nft_net->commit_mutex);