linux-kernel - Re: [syzbot] [trace?] KASAN: slab-use-after-free Read in __free

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Message-ID: <tencent_04E8067F098D2ED5AEC04C86E7DA06EC1206@qq.com>
Date: Tue, 24 Jun 2025 14:10:12 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+daba72c4af9915e9c894@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [trace?] KASAN: slab-use-after-free Read in __free_filter

#syz test

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 08141f105c95..3885aadc434d 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1436,13 +1436,6 @@ static void filter_free_subsystem_filters(struct trace_subsystem_dir *dir,
 
 	INIT_LIST_HEAD(&head->list);
 
-	item = kmalloc(sizeof(*item), GFP_KERNEL);
-	if (!item)
-		goto free_now;
-
-	item->filter = filter;
-	list_add_tail(&item->list, &head->list);
-
 	list_for_each_entry(file, &tr->events, list) {
 		if (file->system != dir)
 			continue;
@@ -1454,6 +1447,13 @@ static void filter_free_subsystem_filters(struct trace_subsystem_dir *dir,
 		event_clear_filter(file);
 	}
 
+	item = kmalloc(sizeof(*item), GFP_KERNEL);
+	if (!item)
+		goto free_now;
+
+	item->filter = filter;
+	list_add_tail(&item->list, &head->list);
+
 	delay_free_filter(head);
 	return;
  free_now: