From mboxrd@z Thu Jan 1 00:00:00 1970 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 E6C47EB64DC for ; Fri, 14 Jul 2023 09:51:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231362AbjGNJvZ (ORCPT ); Fri, 14 Jul 2023 05:51:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236019AbjGNJvC (ORCPT ); Fri, 14 Jul 2023 05:51:02 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC6681BD4 for ; Fri, 14 Jul 2023 02:50:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689328215; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tBjp82gLLLlocN70gzT39Xi/h+/6LoHEroJf4qpzUyQ=; b=Vg/STtZ0aJv8jCD9kFc5pmA6vETyBGgIPTpPBjAioD5tO0Io1QmWJ1cj/iHcL7Q2/11wMt 8HwESYrkWL1SGHomRwxQAu3k/2A7/ZAQfAD+O++a8uhR6hRqwjZtzSPo3twBfZWAnhgUDq FU2fMXMzu+cwN8G6kp3AzYHV/74aBx0= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-638-dAtySRrUNHmm1ql7wZKQwg-1; Fri, 14 Jul 2023 05:50:14 -0400 X-MC-Unique: dAtySRrUNHmm1ql7wZKQwg-1 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-315998d6e7fso1013033f8f.3 for ; Fri, 14 Jul 2023 02:50:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689328213; x=1691920213; h=mime-version:message-id:date:references:in-reply-to:subject:cc:to :from:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tBjp82gLLLlocN70gzT39Xi/h+/6LoHEroJf4qpzUyQ=; b=kSb9HSLbxJe9u5InDJgbs80stXB8dzr6yd7hg9ClnCfKnxd1HjvXJCIA6ydaNLNDns aHI6vJYWc5cUDMzIVL/qgISOGcBejuFtHZLd4KuLilc9wK6l2mXAXgh63zBcmX6jqJHq 65nQINi8JUFdnZMB1hWMg4mqz4ZJ/O7840CGkPoVgA/hip0Ch80Ecw028JIZm+tBNp86 uqf15sm51AEdXfWsYsOKGCNLTPvFSUrFc3W8vXoAPdSGFNcSa5QhlkLHAZyJyACjgpHP AWcv9hcGjESE9meYzUHmQpgGL5kMPrPRoq5BKhoPEPTEgGqseL9lRfkayDvuIbiCAxMX 5P5w== X-Gm-Message-State: ABy/qLbToOOzqHShv/5u1iUXjLkp43lp8JT1X68gnsZFaNiZPWr2miq2 4bux7SsSrYNOmDHdOucKXNCG2tw/nx4l4xaIAn3KepwjetctNaMunN+HxqHWpM1/Nun/EWTF932 QNpAg3AWQt+7T6ItBDQKZ2Wdc X-Received: by 2002:adf:ea10:0:b0:314:35ce:a0e7 with SMTP id q16-20020adfea10000000b0031435cea0e7mr3545416wrm.16.1689328213582; Fri, 14 Jul 2023 02:50:13 -0700 (PDT) X-Google-Smtp-Source: APBJJlFh1wPKblkmTBw8OQ1NLIUngbHtYwtP+MmS66mPVwKsVEsfrpflPboxtBmMk3of1k+PN6KJlg== X-Received: by 2002:adf:ea10:0:b0:314:35ce:a0e7 with SMTP id q16-20020adfea10000000b0031435cea0e7mr3545397wrm.16.1689328213266; Fri, 14 Jul 2023 02:50:13 -0700 (PDT) Received: from localhost ([91.126.32.244]) by smtp.gmail.com with ESMTPSA id g12-20020a5d46cc000000b0031455482d1fsm10372260wrs.47.2023.07.14.02.50.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Jul 2023 02:50:12 -0700 (PDT) From: Javier Martinez Canillas To: Geert Uytterhoeven , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: Re: [PATCH 2/8] drm/dumb-buffers: Fix drm_mode_create_dumb() for bpp < 8 In-Reply-To: <5ba8ac5e465121b646a59487dc75b27017e0c769.1689252746.git.geert@linux-m68k.org> References: <5ba8ac5e465121b646a59487dc75b27017e0c769.1689252746.git.geert@linux-m68k.org> Date: Fri, 14 Jul 2023 11:50:11 +0200 Message-ID: <87o7keu8j0.fsf@minerva.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Geert Uytterhoeven writes: > 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 > --- > Why is drm_mode_create_dumb.size __u64? The test for "args->height > I don't think can be changed since is a DRM_IOCTL_MODE_CREATE_DUMB uAPI ? > U32_MAX / stride" rejects all sizes not fitting in __u32 anyway. Hmm, wonder if should be U64_MAX instead ? > --- > 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 = DIV_ROUND_UP(args->bpp, 8); > if (cpp > U32_MAX / args->width) > return -EINVAL; > - stride = cpp * args->width; > + stride = DIV_ROUND_UP(args->bpp * args->width, 8); > if (args->height > U32_MAX / stride) > return -EINVAL; > Good catch. Reviewed-by: Javier Martinez Canillas -- Best regards, Javier Martinez Canillas Core Platforms Red Hat