linux-kernel - Re: [PATCH 2/2] drivers: tty: vt: vt.c: fixed segmentation fault in vt.c

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Message-ID: <2023110206-robin-feel-d73f@gregkh>
Date:   Thu, 2 Nov 2023 12:42:48 +0100
From:   Greg KH <greg@...ah.com>
To:     dimadrumspro@...il.com
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 2/2] drivers: tty: vt: vt.c: fixed segmentation fault in
 vt.c

Where is patch 1/2?

On Thu, Nov 02, 2023 at 12:39:26PM +0100, dimadrumspro@...il.com wrote:
> From: Dima <dimadrumspro@...il.com>

Is that your full name?

> 
> The previous code lacked proper synchronization, leading to potential data corruption and crashes. Added a spin lock to protect shared variable 'scrollback_delta' to prevent concurrent access.

Please wrap your lines properly, as your editor hinted that you should.

And always run scripts/checkpatch.pl on your patch before submitting it.

> 
> Signed-off-by: Dima <dimadrumspro@...il.com>
> ---
>  drivers/tty/vt/vt.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index 5c47f77804f0..29cf7fe11662 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -301,12 +301,13 @@ static inline unsigned short *screenpos(const struct vc_data *vc, int offset,
>  }
>  
>  /* Called  from the keyboard irq path.. */
> +static DEFINE_SPINLOCK(scrolldelta_lock);
> +
>  static inline void scrolldelta(int lines)
>  {
> -	/* FIXME */
> -	/* scrolldelta needs some kind of consistency lock, but the BKL was
> -	   and still is not protecting versus the scheduled back end */
> +	spin_lock(&scrolldelta_lock);
>  	scrollback_delta += lines;
> +	spin_unlock(&scrolldelta_lock);

How exactly did you test this?  This patch does not do anything that I
can determine.

And what "crashes" have you fixed here?  What "data corruption"?  Your
changelog text does not match this actual change at all from what I can
tell.

thanks,

greg k-h