On Mon, Aug 30, 2021 at 11:30:23AM +0800, tcs.ker...@gmail.com wrote: > From: Haimin Zhang <tcs_ker...@tencent.com> > > yres and vyres can be controlled by user mode parameters, and cause > p->vrows to become a negative value. While this value be passed to real_y > function, the ypos will be out of screen range.This is an out-of-bounds > write bug. > some driver will check xres and yres in fb_check_var callback,but some not > so we add a common check after that callback. > > Signed-off-by: Haimin Zhang <tcs_ker...@tencent.com> > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Does this fix a syzbot crash or how was this discovered? -Daniel > --- > drivers/video/fbdev/core/fbmem.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbmem.c > b/drivers/video/fbdev/core/fbmem.c > index 1c85514..5599372 100644 > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -1013,6 +1013,10 @@ static int fb_check_caps(struct fb_info *info, struct > fb_var_screeninfo *var, > if (ret) > return ret; > > + /* virtual resolution cannot be smaller than visible resolution. */ > + if (var->yres_virtual < var->yres || var->xres_virtual < var->xres) > + return -EINVAL; > + > if ((var->activate & FB_ACTIVATE_MASK) != FB_ACTIVATE_NOW) > return 0; > > -- > 1.8.3.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
