Subject: [PATCH net 2/6] netfilter: nf_tables: release mutex after nft_gc_seq_end from abort path

From: Pablo Neira Ayuso <[email-masked]>
Date: Thu, 4 Apr 2024 12:43:30 +0200

The commit mutex should not be released during the critical section
between nft_gc_seq_begin() and nft_gc_seq_end(), otherwise, async GC
worker could collect expired objects and get the released commit lock
within the same GC sequence.

nf_tables_module_autoload() temporarily releases the mutex to load
module dependencies, then it goes back to replay the transaction again.
Move it at the end of the abort phase after nft_gc_seq_end() is called.

Cc: [email-masked]
Fixes: 720344340fb9 ("netfilter: nf_tables: GC transaction race with abort path")
Reported-by: Kuan-Ting Chen <[email-masked]>
Signed-off-by: Pablo Neira Ayuso <[email-masked]>
---
 net/netfilter/nf_tables_api.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index ffcd3213c335..0d432d0674e1 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -10651,11 +10651,6 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
 		nf_tables_abort_release(trans);
 	}
 
-	if (action == NFNL_ABORT_AUTOLOAD)
-		nf_tables_module_autoload(net);
-	else
-		nf_tables_module_autoload_cleanup(net);
-
 	return err;
 }
 
@@ -10672,6 +10667,14 @@ static int nf_tables_abort(struct net *net, struct sk_buff *skb,
 
 	WARN_ON_ONCE(!list_empty(&nft_net->commit_list));
 
+	/* module autoload needs to happen after GC sequence update because it
+	 * temporarily releases and grabs mutex again.
+	 */
+	if (action == NFNL_ABORT_AUTOLOAD)
+		nf_tables_module_autoload(net);
+	else
+		nf_tables_module_autoload_cleanup(net);
+
 	mutex_unlock(&nft_net->commit_mutex);
 
 	return ret;
-- 
2.30.2