Re: [Qemu-devel] [PATCH v2 2/6] vga: Fix divide-by-zero in vga_update_text

[Gonglei (Arei)]

Hi, Gerd

 What's your opinion about this patch? Thanks,



Best regards,
-Gonglei


> -----Original Message-----
> From: Gonglei (Arei)
> Sent: Wednesday, May 28, 2014 9:22 PM
> To: address@hidden
> Cc: address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden; Huangweidong
> (C); address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> Luonengjun; Gonglei (Arei)
> Subject: [PATCH v2 2/6] vga: Fix divide-by-zero in vga_update_text
> 
> From: Gonglei <address@hidden>
> 
> Spotted by Coverity:
> 
> (20) Event cond_true:  Condition "cursor_visible", taking true branch
> (21) Event cond_true:  Condition "cursor_offset < size", taking true branch
> (22) Event cond_true:  Condition "cursor_offset >= 0", taking true branch
> 
> 2097    if (cursor_visible && cursor_offset < size && cursor_offset >= 0)
> (23) Event divide_by_zero:  In expression "cursor_offset / width",
> division by expression "width" which may be zero has undefined behavior.
> 
> 2098                    dpy_text_cursor(s->con,
> 2099                                    TEXTMODE_X(cursor_offset),
> 2100
> TEXTMODE_Y(cursor_offset));
> 
> Signed-off-by: Gonglei <address@hidden>
> ---
>  hw/display/vga.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/display/vga.c b/hw/display/vga.c
> index 8cd6afe..3c1c6eb 100644
> --- a/hw/display/vga.c
> +++ b/hw/display/vga.c
> @@ -2094,7 +2094,7 @@ static void vga_update_text(void *opaque,
> console_ch_t *chardata)
>              s->cr[VGA_CRTC_CURSOR_START] != s->cursor_start ||
>              s->cr[VGA_CRTC_CURSOR_END] != s->cursor_end ||
> full_update) {
>              cursor_visible = !(s->cr[VGA_CRTC_CURSOR_START] & 0x20);
> -            if (cursor_visible && cursor_offset < size && cursor_offset >=
> 0)
> +            if (cursor_visible && cursor_offset < size && cursor_offset > 0)
>                  dpy_text_cursor(s->con,
>                                  TEXTMODE_X(cursor_offset),
>                                  TEXTMODE_Y(cursor_offset));
> --
> 1.7.12.4
>