Re: [PATCH] tty: vt: check for atomic context in con_write()

[Hillf Danton]

On Sat, 20 Jan 2024 19:34:02 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> syzbot is reporting sleep in atomic context, for gsmld_write() is calling
> con_write() with spinlock held and IRQs disabled.

..

> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -2856,7 +2856,7 @@ static int do_con_write(struct tty_struct *tty, const u8 *buf, int count)
>  	struct vt_notifier_param param;
>  	bool rescan;
>  
> -	if (in_interrupt())
> +	if (in_interrupt() || irqs_disabled())
>  		return count;
>  
>  	console_lock();

Given console_lock(), no sense could be made by calling do_con_write()
with spin lock held at the first place, regardless irq.

> @@ -3314,7 +3314,7 @@ static void con_flush_chars(struct tty_struct *tty)
>  {
>  	struct vc_data *vc;
>  
> -	if (in_interrupt())	/* from flush_to_ldisc */
> +	if (in_interrupt() || irqs_disabled()) /* from flush_to_ldisc */
>  		return;
>  
>  	/* if we race with con_close(), vt may be null */
> -- 
> 2.18.4