[PATCH] fbdev: fbcon: release buffer when fbcon_do_set_font() failed

[Helge Deller]

On 12/5/22 23:10, Tetsuo Handa wrote:
> syzbot is reporting memory leak at fbcon_do_set_font() [1], for
> commit a5a923038d70 ("fbdev: fbcon: Properly revert changes when
> vc_resize() failed") missed that the buffer might be newly allocated
> by fbcon_set_font().
>
> Link: https://syzkaller.appspot.com/bug?extid=25bdb7b1703639abd498 [1]
> Reported-by: syzbot <syzbot+25bdb7b1703639abd498 at syzkaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
> Tested-by: syzbot <syzbot+25bdb7b1703639abd498 at syzkaller.appspotmail.com>
> Fixes: a5a923038d70 ("fbdev: fbcon: Properly revert changes when vc_resize() failed")

applied.
Thanks!

Helge

> ---
>   drivers/video/fbdev/core/fbcon.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 098b62f7b701..8363f3b2b452 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -2450,7 +2450,8 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
>
>   	if (userfont) {
>   		p->userfont = old_userfont;
> -		REFCOUNT(data)--;
> +		if (--REFCOUNT(data) == 0)
> +			kfree(data - FONT_EXTRA_WORDS * sizeof(int));
>   	}
>
>   	vc->vc_font.width = old_width;