From nobody Sat Feb 7 15:36:14 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 0225FC49EC3 for ; Tue, 23 Aug 2022 10:23:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352818AbiHWKXj (ORCPT ); Tue, 23 Aug 2022 06:23:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353420AbiHWKL2 (ORCPT ); Tue, 23 Aug 2022 06:11:28 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E92A46B8C4; Tue, 23 Aug 2022 01:56:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 66E0D614E7; Tue, 23 Aug 2022 08:56:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73641C433D6; Tue, 23 Aug 2022 08:56:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661245002; bh=QJRKZeqWyHOAMgpIQr673Jjz8RQb1Y0LVJw0ylK1rRM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uZjzfcVj17Q2NjcWjUd6657A6LQhoLhdtZiOVMBRVbyuHxxp0D18XeMmzEASClMXM XXQFWDEK0iT9VZAdn3Tg5XzoeiR6NSC8SvPVFkCntd1ZjnHQktAulmS8zj7T4zi0Or XTd149syJ47LdE7B7rEFOfre7UsoCbN4FRut+3PQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Zheyu Ma , Helge Deller , Sasha Levin Subject: [PATCH 4.14 228/229] video: fbdev: i740fb: Check the argument of i740_calc_vclk() Date: Tue, 23 Aug 2022 10:26:29 +0200 Message-Id: <20220823080101.775619886@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080053.202747790@linuxfoundation.org> References: <20220823080053.202747790@linuxfoundation.org> User-Agent: quilt/0.67 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" From: Zheyu Ma [ Upstream commit 40bf722f8064f50200b8c4f8946cd625b441dda9 ] Since the user can control the arguments of the ioctl() from the user space, under special arguments that may result in a divide-by-zero bug. If the user provides an improper 'pixclock' value that makes the argumet of i740_calc_vclk() less than 'I740_RFREQ_FIX', it will cause a divide-by-zero bug in: drivers/video/fbdev/i740fb.c:353 p_best =3D min(15, ilog2(I740_MAX_VCO_= FREQ / (freq / I740_RFREQ_FIX))); The following log can reveal it: divide error: 0000 [#1] PREEMPT SMP KASAN PTI RIP: 0010:i740_calc_vclk drivers/video/fbdev/i740fb.c:353 [inline] RIP: 0010:i740fb_decode_var drivers/video/fbdev/i740fb.c:646 [inline] RIP: 0010:i740fb_set_par+0x163f/0x3b70 drivers/video/fbdev/i740fb.c:742 Call Trace: fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1034 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189 Fix this by checking the argument of i740_calc_vclk() first. Signed-off-by: Zheyu Ma Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/i740fb.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/video/fbdev/i740fb.c b/drivers/video/fbdev/i740fb.c index 7bc5f6056c77..4147a9534179 100644 --- a/drivers/video/fbdev/i740fb.c +++ b/drivers/video/fbdev/i740fb.c @@ -399,7 +399,7 @@ static int i740fb_decode_var(const struct fb_var_screen= info *var, u32 xres, right, hslen, left, xtotal; u32 yres, lower, vslen, upper, ytotal; u32 vxres, xoffset, vyres, yoffset; - u32 bpp, base, dacspeed24, mem; + u32 bpp, base, dacspeed24, mem, freq; u8 r7; int i; =20 @@ -641,7 +641,12 @@ static int i740fb_decode_var(const struct fb_var_scree= ninfo *var, par->atc[VGA_ATC_OVERSCAN] =3D 0; =20 /* Calculate VCLK that most closely matches the requested dot clock */ - i740_calc_vclk((((u32)1e9) / var->pixclock) * (u32)(1e3), par); + freq =3D (((u32)1e9) / var->pixclock) * (u32)(1e3); + if (freq < I740_RFREQ_FIX) { + fb_dbg(info, "invalid pixclock\n"); + freq =3D I740_RFREQ_FIX; + } + i740_calc_vclk(freq, par); =20 /* Since we program the clocks ourselves, always use VCLK2. */ par->misc |=3D 0x0C; --=20 2.35.1