From patchwork Thu Oct 18 10:02:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Boris Brezillon X-Patchwork-Id: 10646965 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C11DC17D4 for ; Thu, 18 Oct 2018 10:02:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A747E28880 for ; Thu, 18 Oct 2018 10:02:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9B0E7288BC; Thu, 18 Oct 2018 10:02:58 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 3B6A728880 for ; Thu, 18 Oct 2018 10:02:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 21C2E89C5E; Thu, 18 Oct 2018 10:02:55 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail.bootlin.com (mail.bootlin.com [62.4.15.54]) by gabe.freedesktop.org (Postfix) with ESMTP id 72D6A89C5E for ; Thu, 18 Oct 2018 10:02:54 +0000 (UTC) Received: by mail.bootlin.com (Postfix, from userid 110) id 637CD2090A; Thu, 18 Oct 2018 12:02:53 +0200 (CEST) Received: from localhost.localdomain (AAubervilliers-681-1-25-52.w90-88.abo.wanadoo.fr [90.88.145.52]) by mail.bootlin.com (Postfix) with ESMTPSA id 2EF2D20723; Thu, 18 Oct 2018 12:02:53 +0200 (CEST) From: Boris Brezillon To: Maxime Ripard , Chen-Yu Tsai Subject: [PATCH v2] drm/sun4i: Fix an ulong overflow in the dotclock driver Date: Thu, 18 Oct 2018 12:02:50 +0200 Message-Id: <20181018100250.12565-1-boris.brezillon@bootlin.com> X-Mailer: git-send-email 2.14.1 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Boris Brezillon , stable@vger.kernel.org, dri-devel@lists.freedesktop.org MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP The calculated ideal rate can easily overflow an unsigned long, thus making the best div selection buggy as soon as no ideal match is found before the overflow occurs. Fixes: 4731a72df273 ("drm/sun4i: request exact rates to our parents") Cc: Signed-off-by: Boris Brezillon Acked-by: Maxime Ripard --- Changes in v2: - Add a comment to explain why we bail out after an overflow - Add Maxime ack - Use a goto instead of a break --- drivers/gpu/drm/sun4i/sun4i_dotclock.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/sun4i/sun4i_dotclock.c b/drivers/gpu/drm/sun4i/sun4i_dotclock.c index e36004fbe453..2a15f2f9271e 100644 --- a/drivers/gpu/drm/sun4i/sun4i_dotclock.c +++ b/drivers/gpu/drm/sun4i/sun4i_dotclock.c @@ -81,9 +81,19 @@ static long sun4i_dclk_round_rate(struct clk_hw *hw, unsigned long rate, int i; for (i = tcon->dclk_min_div; i <= tcon->dclk_max_div; i++) { - unsigned long ideal = rate * i; + u64 ideal = (u64)rate * i; unsigned long rounded; + /* + * ideal has overflowed the max value that can be stored in an + * unsigned long, and every clk operation we might do on a + * truncated u64 value will give us incorrect results. + * Let's just stop there since bigger dividers will result in + * the same overflow issue. + */ + if (ideal > ULONG_MAX) + goto out; + rounded = clk_hw_round_rate(clk_hw_get_parent(hw), ideal);