drm/fb-helper: Fix height, width, and accel_flags in fb_var

Fbtest contains some very simple validation of the fbdev userspace API
contract.  When used with shmob-drm, it reports the following warnings
and errors:

    height changed from 68 to 0
    height was rounded down
    width changed from 111 to 0
    width was rounded down
    accel_flags changed from 0 to 1

The first part happens because __fill_var() resets the physical
dimensions of the first connector, as filled in by drm_setup_crtcs_fb().
Fix this by retaining the original values.

The last part happens because __fill_var() forces the FB_ACCELF_TEXT
flag on, while fbtest disables all acceleration on purpose, so it can
draw safely to the frame buffer.  Fix this by setting accel_flags to
zero, as DRM does not implement any text console acceleration.
Note that this issue can also be seen in the output of fbset, which
reports "accel true".

Fixes: ee4cce0a8f03a333 ("drm/fb-helper: fix input validation gaps in check_var")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/57e6b334dae8148b1b8ae6ef308ce9a83810a850.1684854344.git.geert+renesas@glider.be

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 6bb1b8b..fd27f19 100644 (file)
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1545,17 +1545,19 @@ static void drm_fb_helper_fill_pixel_fmt(struct fb_var_screeninfo *var,
        }
 }
 
-static void __fill_var(struct fb_var_screeninfo *var,
+static void __fill_var(struct fb_var_screeninfo *var, struct fb_info *info,
                       struct drm_framebuffer *fb)
 {
        int i;
 
        var->xres_virtual = fb->width;
        var->yres_virtual = fb->height;
-       var->accel_flags = FB_ACCELF_TEXT;
+       var->accel_flags = 0;
        var->bits_per_pixel = drm_format_info_bpp(fb->format, 0);
 
-       var->height = var->width = 0;
+       var->height = info->var.height;
+       var->width = info->var.width;
+
        var->left_margin = var->right_margin = 0;
        var->upper_margin = var->lower_margin = 0;
        var->hsync_len = var->vsync_len = 0;
@@ -1618,7 +1620,7 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
                return -EINVAL;
        }
 
-       __fill_var(var, fb);
+       __fill_var(var, info, fb);
 
        /*
         * fb_pan_display() validates this, but fb_set_par() doesn't and just
@@ -2074,7 +2076,7 @@ static void drm_fb_helper_fill_var(struct fb_info *info,
        info->pseudo_palette = fb_helper->pseudo_palette;
        info->var.xoffset = 0;
        info->var.yoffset = 0;
-       __fill_var(&info->var, fb);
+       __fill_var(&info->var, info, fb);
        info->var.activate = FB_ACTIVATE_NOW;
 
        drm_fb_helper_fill_pixel_fmt(&info->var, format);