From nobody Mon Feb 9 00:26:17 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 542A7EB64DD for ; Thu, 13 Jul 2023 13:17:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234858AbjGMNR4 (ORCPT ); Thu, 13 Jul 2023 09:17:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234806AbjGMNRb (ORCPT ); Thu, 13 Jul 2023 09:17:31 -0400 Received: from michel.telenet-ops.be (michel.telenet-ops.be [IPv6:2a02:1800:110:4::f00:18]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A01E270D for ; Thu, 13 Jul 2023 06:17:25 -0700 (PDT) Received: from ramsan.of.borg ([IPv6:2a02:1810:ac12:ed40:6264:77e5:42e2:477d]) by michel.telenet-ops.be with bizsmtp id LdHN2A00Z3wy6xv06dHNad; Thu, 13 Jul 2023 15:17:23 +0200 Received: from rox.of.borg ([192.168.97.57]) by ramsan.of.borg with esmtp (Exim 4.95) (envelope-from ) id 1qJwC3-001Gqq-0u; Thu, 13 Jul 2023 15:17:22 +0200 Received: from geert by rox.of.borg with local (Exim 4.95) (envelope-from ) id 1qJwCA-00GWyY-N9; Thu, 13 Jul 2023 15:17:22 +0200 From: Geert Uytterhoeven To: Javier Martinez Canillas , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH 2/8] drm/dumb-buffers: Fix drm_mode_create_dumb() for bpp < 8 Date: Thu, 13 Jul 2023 15:17:10 +0200 Message-Id: <5ba8ac5e465121b646a59487dc75b27017e0c769.1689252746.git.geert@linux-m68k.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" drm_mode_create_dumb() calculates the number of characters per pixel from the number of bits per pixel by rounding up, which is not correct as the actual value of cpp may be non-integer. While we do not need to care here about complex formats like YUV, bpp < 8 is a valid use case. - The overflow check for the buffer width is not correct if bpp < 8. However, it doesn't hurt, as widths larger than U32_MAX / 8 should not happen for real anyway. Add a comment to clarify. - Calculating the stride from the number of characters per pixel is not correct. Fix this by calculating it from the number of bits per pixel instead. Signed-off-by: Geert Uytterhoeven Reviewed-by: Javier Martinez Canillas --- Why is drm_mode_create_dumb.size __u64? The test for "args->height > U32_MAX / stride" rejects all sizes not fitting in __u32 anyway. --- drivers/gpu/drm/drm_dumb_buffers.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_dumb_buffers.c b/drivers/gpu/drm/drm_dumb_= buffers.c index 70032bba1c97e787..21a04c32a5e3d785 100644 --- a/drivers/gpu/drm/drm_dumb_buffers.c +++ b/drivers/gpu/drm/drm_dumb_buffers.c @@ -71,10 +71,11 @@ int drm_mode_create_dumb(struct drm_device *dev, /* overflow checks for 32bit size calculations */ if (args->bpp > U32_MAX - 8) return -EINVAL; + /* Incorrect (especially if bpp < 8), but doesn't hurt much */ cpp =3D DIV_ROUND_UP(args->bpp, 8); if (cpp > U32_MAX / args->width) return -EINVAL; - stride =3D cpp * args->width; + stride =3D DIV_ROUND_UP(args->bpp * args->width, 8); if (args->height > U32_MAX / stride) return -EINVAL; =20 --=20 2.34.1