linux-kernel - Re: [PATCH 07/11] tty: vt: replace BUG_ON() by WARN_ON

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Message-ID: <239b3d75-6186-3c3c-91bb-7ec46545f345@linux.intel.com>
Date:   Thu, 12 Jan 2023 11:42:53 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc:     gregkh@...uxfoundation.org, Kees Cook <keescook@...omium.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/11] tty: vt: replace BUG_ON() by WARN_ON_ONCE()

On Thu, 12 Jan 2023, Jiri Slaby (SUSE) wrote:

> No need to panic in vc_uniscr_copy_line(), just warn. This should never
> happen though, as vc_uniscr_check() is supposed to be called before
> vc_uniscr_copy_line(). And the former checks vc->vc_uni_lines already.
> 
> In any case, use _ONCE as vc_uniscr_copy_line() is called repeatedly for
> each line. So don't flood the logs, just in case.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> ---
>  drivers/tty/vt/vt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index 119b3eafef59..db72375141b0 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -535,7 +535,8 @@ void vc_uniscr_copy_line(const struct vc_data *vc, void *dest, bool viewed,
>  	int offset = row * vc->vc_size_row + col * 2;
>  	unsigned long pos;
>  
> -	BUG_ON(!uni_lines);
> +	if (WARN_ON_ONCE(!uni_lines))
> +		return;
>  
>  	pos = (unsigned long)screenpos(vc, offset, viewed);
>  	if (pos >= vc->vc_origin && pos < vc->vc_scr_end) {
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.