linux-kernel - Re: [syzbot] [input?] possible deadlock in input_ff

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Message-ID: <20250106110825.1430-1-hdanton@sina.com>
Date: Mon,  6 Jan 2025 19:08:24 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+ed7c6209f62eba1565aa@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [input?] possible deadlock in input_ff_flush

On Sun, 05 Jan 2025 04:40:19 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g..
> git tree:       upstream
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17bd56df980000

#syz test

--- x/drivers/input/input.c
+++ y/drivers/input/input.c
@@ -642,17 +642,11 @@ EXPORT_SYMBOL(input_open_device);
 int input_flush_device(struct input_handle *handle, struct file *file)
 {
 	struct input_dev *dev = handle->dev;
-	int retval;
-
-	retval = mutex_lock_interruptible(&dev->mutex);
-	if (retval)
-		return retval;
 
 	if (dev->flush)
-		retval = dev->flush(dev, file);
+		return dev->flush(dev, file);
 
-	mutex_unlock(&dev->mutex);
-	return retval;
+	return 0;
 }
 EXPORT_SYMBOL(input_flush_device);
 
--- x/mm/vmstat.c
+++ y/mm/vmstat.c
@@ -2122,9 +2122,11 @@ static void __init start_shepherd_timer(
 {
 	int cpu;
 
-	for_each_possible_cpu(cpu)
+	for_each_possible_cpu(cpu) {
 		INIT_DEFERRABLE_WORK(per_cpu_ptr(&vmstat_work, cpu),
 			vmstat_update);
+		disable_delayed_work(per_cpu_ptr(&vmstat_work, cpu));
+	}
 
 	schedule_delayed_work(&shepherd,
 		round_jiffies_relative(sysctl_stat_interval));
--