Merge: CVE-2024-45018: netfilter: flowtable: initialise extack before use

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5174

JIRA: https://issues.redhat.com/browse/RHEL-58544  
CVE: CVE-2024-45018

```
netfilter: flowtable: initialise extack before use

Fix missing initialisation of extack in flow offload.

Fixes: c29f74e ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Donald Hunter <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>
(cherry picked from commit e976713)
```

Signed-off-by: CKI Backport Bot <[email protected]>

Approved-by: Florian Westphal <[email protected]>
Approved-by: Antoine Tenart <[email protected]>
Approved-by: CKI KWF Bot <[email protected]>

Merged-by: Rado Vrbovsky <[email protected]>

Author: emmil

net/netfilter/nf_flow_table_offload.c

@@ -834,8 +834,8 @@ static int nf_flow_offload_tuple(struct nf_flowtable *flowtable,
 				 struct list_head *block_cb_list)
 {
 	struct flow_cls_offload cls_flow = {};
+	struct netlink_ext_ack extack = {};
 	struct flow_block_cb *block_cb;
-	struct netlink_ext_ack extack;
 	__be16 proto = ETH_P_ALL;
 	int err, i = 0;