From 8a5bbf327aa16025c78491266a6425807c7fbee0 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 21 Oct 2016 15:15:40 +0100 Subject: [PATCH] drm: Use u64 for intermediate dotclock calculations MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit We have reached the era where monitor bandwidths now exceed 31bits in frequency calculations, though as we stored them in kHz units we are safe from overflow in the modelines for some time. [ 48.723720] UBSAN: Undefined behaviour in ../drivers/gpu/drm/drm_modes.c:325:49 [ 48.726943] signed integer overflow: [ 48.728503] 2240 * 1000000 cannot be represented in type 'int' Reported-by: Martin Liška Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98372 Signed-off-by: Chris Wilson Reviewed-by: Alex Deucher Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20161021141540.26837-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/drm_modes.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c index 173b7d335834..f64ac86deb84 100644 --- a/drivers/gpu/drm/drm_modes.c +++ b/drivers/gpu/drm/drm_modes.c @@ -165,6 +165,7 @@ struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay, unsigned int vfieldrate, hperiod; int hdisplay_rnd, hmargin, vdisplay_rnd, vmargin, vsync; int interlace; + u64 tmp; /* allocate the drm_display_mode structure. If failure, we will * return directly @@ -322,8 +323,11 @@ struct drm_display_mode *drm_cvt_mode(struct drm_device *dev, int hdisplay, drm_mode->vsync_end = drm_mode->vsync_start + vsync; } /* 15/13. Find pixel clock frequency (kHz for xf86) */ - drm_mode->clock = drm_mode->htotal * HV_FACTOR * 1000 / hperiod; - drm_mode->clock -= drm_mode->clock % CVT_CLOCK_STEP; + tmp = drm_mode->htotal; /* perform intermediate calcs in u64 */ + tmp *= HV_FACTOR * 1000; + do_div(tmp, hperiod); + tmp -= drm_mode->clock % CVT_CLOCK_STEP; + drm_mode->clock = tmp; /* 18/16. Find actual vertical frame frequency */ /* ignore - just set the mode flag for interlaced */ if (interlaced) { -- 2.20.1