On Mon, Aug 30, 2021 at 11:30:23AM +0800, tcs.kernel@gmail.com wrote:
From: Haimin Zhang tcs_kernel@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_kernel@tencent.com Signed-off-by: Tetsuo Handa penguin-kernel@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