linux-kernel - Re: [PATCH riscv64] kobject: fix WARNING in input_register

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Message-ID: <2024020812-snowbound-version-6bfa@gregkh>
Date: Thu, 8 Feb 2024 10:56:00 +0000
From: Greg KH <gregkh@...uxfoundation.org>
To: Edward Adam Davis <eadavis@...com>
Cc: syzbot+8e41bb0c055b209ebbf4@...kaller.appspotmail.com,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, rafael@...nel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH riscv64] kobject: fix WARNING in input_register_device

On Thu, Feb 08, 2024 at 06:46:55PM +0800, Edward Adam Davis wrote:
> The input_add_uevent_modalias_var()->input_print_modalias() will add 1684 bytes
> of data to env, which will result in insufficient memory allocated to the buf 
> members of env.

What is "env"?  And can you wrap your lines at 72 columns please?

> Reported-and-tested-by: syzbot+8e41bb0c055b209ebbf4@...kaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
>  include/linux/kobject.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/kobject.h b/include/linux/kobject.h
> index c30affcc43b4..74b37b6459cd 100644
> --- a/include/linux/kobject.h
> +++ b/include/linux/kobject.h
> @@ -30,7 +30,7 @@
>  
>  #define UEVENT_HELPER_PATH_LEN		256
>  #define UEVENT_NUM_ENVP			64	/* number of env pointers */
> -#define UEVENT_BUFFER_SIZE		2048	/* buffer for the variables */
> +#define UEVENT_BUFFER_SIZE		2560	/* buffer for the variables */

That's an odd number, why that?  Why not just a page?  What happens if
some other path wants more?

And what's causing the input stack to have so many variables all of a
sudden, what changed to cause this?  Is this a bugfix for a specific
commit that needs to be backported to older kernels?  Why did this
buffer size all of a sudden be too small?

thanks,

greg k-h