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 X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8BF0CC4708A for ; Thu, 27 May 2021 16:27:47 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 53D6E61003 for ; Thu, 27 May 2021 16:27:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 53D6E61003 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=jlekstrand.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2241B6F45D; Thu, 27 May 2021 16:27:29 +0000 (UTC) Received: from mail-pf1-x42b.google.com (mail-pf1-x42b.google.com [IPv6:2607:f8b0:4864:20::42b]) by gabe.freedesktop.org (Postfix) with ESMTPS id BE72D6F458 for ; Thu, 27 May 2021 16:27:24 +0000 (UTC) Received: by mail-pf1-x42b.google.com with SMTP id c12so991243pfl.3 for ; Thu, 27 May 2021 09:27:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=jlekstrand-net.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=AIDizxQ4UDUcjVr9hejmmeBEYh5jxyhNoh2wE4chMAo=; b=smTS9ICJ8Sip1NsKNWIkLO+F95kqyBVsHhaOMDgwx/fvz37vURWeYI1SpcqhQGKKCA EbfN1m2qwBjquj5ct9hB9R80k7VxioYoSIT2Rf+rAqze33MT74r4pqtHrk7GdGc4Vxoj bAy424a2dk5h3EyNUie95OntlZebehh3OncRQ0xxqoXNmMF094+lBOeCbmORTtXQnawe 2RBXZlihJOUGDB4puxQSKdGy9lZGpCqaHDOYBvW9ygd1CbAKzgXeYzRpR71NXFPLN7Ml uRerM3gP95B/rBu0Ud9iXa1Q1l5dgrh2+EPuuIgGTRNfL0fAd6+9arcEKHtmlMccLCUQ qpFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=AIDizxQ4UDUcjVr9hejmmeBEYh5jxyhNoh2wE4chMAo=; b=tmcJNyEzJ/uDh05eEGI2IhJdMyhNIUrWwLkTXDPHTKZjySdyuBunJbHtO3fbgeonV7 wnSZPl5hQYEQx6ag63pVwe7wJiM9gjIHyGdksHxgE7eZIUXMqhYTQf6cy6DWBlG6KO3A Zs1Cq0PZc7dKNcuwAx0oLDFkfJkJxEFztLrukxfH5p/ceZNZ6ba4z4rIen/9YRDrULzs CzuUaoRIq1y1wuiLposfiHTyEaLswLZDwleUtYMyj20vo/IsSAqjZNJUW9NrVtUYoIa0 zoZHirXeuUClNwWQryjHOG3q5G4K3YM6oh+LRnetbGIoifM83fhz9IqIA5J4ZzmqgD8M woyQ== X-Gm-Message-State: AOAM530mK0XdpSmdRj0/FCBnByiUye8QPVYZ3VQ6xwciG8YwWTfOvYRQ OTj8knwqMreLoQq8wtUpykbHrg== X-Google-Smtp-Source: ABdhPJyK1EJ2dwQlTNhqf/FlfmQbzv0sbE7cUTNzJFYA9rnnZ/WOLdUG6cnuUU0jX5PDrjvOtuT0Ig== X-Received: by 2002:a62:d0c2:0:b029:2d9:529f:f4ef with SMTP id p185-20020a62d0c20000b02902d9529ff4efmr4543244pfg.41.1622132843384; Thu, 27 May 2021 09:27:23 -0700 (PDT) Received: from omlet.com ([134.134.139.83]) by smtp.gmail.com with ESMTPSA id h9sm2298711pja.42.2021.05.27.09.27.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 May 2021 09:27:23 -0700 (PDT) From: Jason Ekstrand To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH 20/29] drm/i915/gem: Make an alignment check more sensible Date: Thu, 27 May 2021 11:26:41 -0500 Message-Id: <20210527162650.1182544-21-jason@jlekstrand.net> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210527162650.1182544-1-jason@jlekstrand.net> References: <20210527162650.1182544-1-jason@jlekstrand.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jason Ekstrand Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" What we really want to check is that size of the engines array, i.e. args->size - sizeof(*user) is divisible by the element size, i.e. sizeof(*user->engines) because that's what's required for computing the array length right below the check. However, we're currently not doing this and instead doing a compile-time check that sizeof(*user) is divisible by sizeof(*user->engines) and avoiding the subtraction. As far as I can tell, the only reason for the more confusing pair of checks is to avoid a single subtraction of a constant. The other thing the BUILD_BUG_ON might be trying to implicitly check is that offsetof(user->engines) == sizeof(*user) and we don't have any weird padding throwing us off. However, that's not the check it's doing and it's not even a reliable way to do that check. Signed-off-by: Jason Ekstrand --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 12a148ba421b6..cf7c281977a3e 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -1758,9 +1758,8 @@ set_engines(struct i915_gem_context *ctx, goto replace; } - BUILD_BUG_ON(!IS_ALIGNED(sizeof(*user), sizeof(*user->engines))); if (args->size < sizeof(*user) || - !IS_ALIGNED(args->size, sizeof(*user->engines))) { + !IS_ALIGNED(args->size - sizeof(*user), sizeof(*user->engines))) { drm_dbg(&i915->drm, "Invalid size for engine array: %d\n", args->size); return -EINVAL; -- 2.31.1