Hi Daniel, CC vkmsdrm maintainer Thanks for your patch! On Tue, Apr 4, 2023 at 2:36 PM Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > There's a few reasons the kernel should not spam dmesg on bad > userspace ioctl input: > - at warning level it results in CI false positives > - it allows userspace to drown dmesg output, potentially hiding real > issues. > > None of the other generic EINVAL checks report in the > FBIOPUT_VSCREENINFO ioctl do this, so it's also inconsistent. > > I guess the intent of the patch which introduced this warning was that > the drivers ->fb_check_var routine should fail in that case. Reality > is that there's too many fbdev drivers and not enough people > maintaining them by far, and so over the past few years we've simply > handled all these validation gaps by tighning the checks in the core, > because that's realistically really all that will ever happen. > > Reported-by: syzbot+20dcf81733d43ddff661@xxxxxxxxxxxxxxxxxxxxxxxxx > Link: https://syzkaller.appspot.com/bug?id=c5faf983bfa4a607de530cd3bb008888bf06cefc WARNING: fbcon: Driver 'vkmsdrmfb' missed to adjust virtual screen size (0x0 vs. 64x768) This is a bug in the vkmsdrmfb driver and/or DRM helpers. The message was added to make sure the individual drivers are fixed. Perhaps it should be changed to BUG() instead, so dmesg output cannot be drown? > Fixes: 6c11df58fd1a ("fbmem: Check virtual screen sizes in fb_set_var()") > Cc: Helge Deller <deller@xxxxxx> > Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx # v5.4+ > Cc: Daniel Vetter <daniel@xxxxxxxx> > Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> NAKed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -1021,10 +1021,6 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) > /* verify that virtual resolution >= physical resolution */ > if (var->xres_virtual < var->xres || > var->yres_virtual < var->yres) { > - pr_warn("WARNING: fbcon: Driver '%s' missed to adjust virtual screen size (%ux%u vs. %ux%u)\n", > - info->fix.id, > - var->xres_virtual, var->yres_virtual, > - var->xres, var->yres); > return -EINVAL; > } Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
