Dear Thomas, Thank you for the kind advice. In fact, I notice there was a discussion regarding whether to put the check in each individual driver or solve this problem as a whole as you suggested. The conclusion is that it is better to keep the check per driver rather than in the caller. Related discussions are here: https://lore.kernel.org/all/YXclZQGFTr1NFjbc@xxxxxxxxxxxx/ https://lore.kernel.org/all/YPgbHMtLQqb1kP0l@xxxxxxxxxxxx/ https://lore.kernel.org/all/20220404084723.79089-1-zheyuma97@xxxxxxxxx/ Thanks, Wei ------ Original Message ------ >From "Thomas Zimmermann" <tzimmermann@xxxxxxx> To "Wei Chen" <harperchen1110@xxxxxxxxx>; deller@xxxxxx Cc linux-fbdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx Date 2023/3/15 18:25:52 Subject Re: [PATCH] fbdev: au1200fb: Fix potential divide by zero On Wed, 15 Mar 2023 at 18:25, Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > Hi, > > thanks for looking through these drivers. > > Am 15.03.23 um 10:22 schrieb Wei Chen: > > var->pixclock can be assigned to zero by user. Without > > proper check, divide by zero would occur when invoking > > macro PICOS2KHZ in au1200fb_fb_check_var. > > > > Error out if var->pixclock is zero. > > > > Signed-off-by: Wei Chen <harperchen1110@xxxxxxxxx> > > --- > > drivers/video/fbdev/au1200fb.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/video/fbdev/au1200fb.c b/drivers/video/fbdev/au1200fb.c > > index 81c315454428..b6b22fa4a8a0 100644 > > --- a/drivers/video/fbdev/au1200fb.c > > +++ b/drivers/video/fbdev/au1200fb.c > > @@ -1040,6 +1040,9 @@ static int au1200fb_fb_check_var(struct fb_var_screeninfo *var, > > u32 pixclock; > > int screen_size, plane; > > > > + if (!var->pixclock) > > + return -EINVAL; > > + > > Instead of the whale-a-mole approach of fixing individual drivers, could > this be solved by testing in fb_set_var [1] and fb_try_mode.? [2] > > Best regards > Thomas > > [1] > https://elixir.bootlin.com/linux/latest/source/drivers/video/fbdev/core/fbmem.c#L958 > [2] > https://elixir.bootlin.com/linux/latest/source/drivers/video/fbdev/core/modedb.c#L567 > > > plane = fbdev->plane; > > > > /* Make sure that the mode respect all LCD controller and > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Ivo Totev
