linux-kernel - Re: kernel v6.7 warn in add_uevent

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Message-ID: <2024120410-overact-rocking-fe93@gregkh>
Date: Wed, 4 Dec 2024 10:41:52 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: wzs <wangzhengshu39@...il.com>
Cc: rafael@...nel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: kernel v6.7 warn in add_uevent_var: buffer size too small

On Wed, Dec 04, 2024 at 05:29:26PM +0800, wzs wrote:
> Hello,
> when fuzzing the Linux kernel 6.7.0,
> the following crash was triggered.
> 
> kernel config :  https://pastebin.com/3JeQFdUr
> console output : https://pastebin.com/9ADtBQtP
> 
> Basically, we use gadget module to simulate the connection and interaction
> process of a USB device
> (device type code : 0003, vendor id : 046D, product id : C312, serial
> number : 27B4, with function : input event).
> 
> It seems to be caused by a mismatch between the uevent's environmental
> limit and the buffer size used to receive the uevent, which triggers such
> kernel warning.
> 
> The crash report is as follow:
> 、、、
>  [203835.102225] input: wingfuz Keyboard as
> /devices/platform/dummy_hcd.0/usb3/3-1/3-1:1.0/0003:046D:C312.27B4/input/input5893
>  [203835.155527] ------------[ cut here ]------------
>  [203835.155533] add_uevent_var: buffer size too small
>  [203835.162092] WARNING: CPU: 11 PID: 57434 at lib/kobject_uevent.c:671
> add_uevent_var+0x2fe/0x390

I think this is already fixed in newer kernel versions.  6.7.0 is very
old and obsolete.  Can you test this on 6.12.1?

thanks,

greg k-h