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: [email protected] Link: https://syzkaller.appspot.com/bug?id=c5faf983bfa4a607de530cd3bb008888bf06cefc Fixes: 6c11df58fd1a ("fbmem: Check virtual screen sizes in fb_set_var()") Cc: Helge Deller <[email protected]> Cc: Geert Uytterhoeven <[email protected]> Cc: [email protected] # v5.4+ Cc: Daniel Vetter <[email protected]> Cc: Javier Martinez Canillas <[email protected]> Cc: Thomas Zimmermann <[email protected]> Signed-off-by: Daniel Vetter <[email protected]> --- drivers/video/fbdev/core/fbmem.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 875541ff185b..9757f4bcdf57 100644 --- 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; } -- 2.40.0
