linux-kernel - Re: [syzbot] [kernfs?] [usb?] WARNING in kernfs

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Date: Thu, 16 May 2024 22:27:48 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+2f44671e54488d20f0e6@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [kernfs?] [usb?] WARNING in kernfs_get (5)

On Tue, 14 May 2024 08:44:43 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    26dd54d03cd9 Add linux-next specific files for 20240514
> git tree:       linux-next
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14b06900980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git  26dd54d03cd9

--- l/drivers/base/firmware_loader/fallback.c
+++ f/drivers/base/firmware_loader/fallback.c
@@ -64,6 +64,7 @@ void kill_pending_fw_fallback_reqs(bool
 	mutex_unlock(&fw_lock);
 }
 
+static DEFINE_MUTEX(fw_load_sysfs_mutex);
 /**
  * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism
  * @fw_sysfs: firmware sysfs information for the firmware to load
@@ -82,6 +83,7 @@ static int fw_load_sysfs_fallback(struct
 		fw_priv->is_paged_buf = true;
 
 	dev_set_uevent_suppress(f_dev, true);
+	mutex_lock(&fw_load_sysfs_mutex);
 
 	retval = device_add(f_dev);
 	if (retval) {
@@ -124,6 +126,7 @@ out:
 	device_del(f_dev);
 err_put_dev:
 	put_device(f_dev);
+	mutex_unlock(&fw_load_sysfs_mutex);
 	return retval;
 }
 
--