From nobody Sun Feb 8 09:14:47 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 04857C32772 for ; Tue, 23 Aug 2022 10:04:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352074AbiHWKEX (ORCPT ); Tue, 23 Aug 2022 06:04:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348019AbiHWJ70 (ORCPT ); Tue, 23 Aug 2022 05:59:26 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA1B0A1D77; Tue, 23 Aug 2022 01:48:05 -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 E96A161517; Tue, 23 Aug 2022 08:48:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D066BC433D7; Tue, 23 Aug 2022 08:48:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661244484; bh=wTxpJY+B15fweHM9fBmoHGEdTlkxs3vXb9rtlhbnw7k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2LpBY1G3OjsVCwZh+3mf6tgtB+lygOAQT/uPPs7liC9EBlwqkRfyf8kFpxPqh/q0r fWEHAT2CXu1w5zLYA4Ez2y6KU1BoWHXPa6UMDuxuDi7UIBhTqC7ZD3p9sCIzsFsnM0 Xr1vY/en0tlw0VdYzw64DSNy2vhN4C27em1UKw3A= 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 4.14 144/229] video: fbdev: arkfb: Fix a divide-by-zero bug in ark_set_pixclock() Date: Tue, 23 Aug 2022 10:25:05 +0200 Message-Id: <20220823080058.812832833@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 2f1c4523f7a3aaabe7e53d3ebd378292947e95c8 ] 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 in: drivers/video/fbdev/arkfb.c:784: ark_set_pixclock(info, (hdiv * info->var= .pixclock) / hmul); with hdiv=3D1, pixclock=3D1 and hmul=3D2 you end up with (1*1)/2 =3D (int) = 0. and then in: drivers/video/fbdev/arkfb.c:504: rv =3D dac_set_freq(par->dac, 0, 1000000= 000 / pixclock); we'll get a division-by-zero. The following log can reveal it: divide error: 0000 [#1] PREEMPT SMP KASAN PTI RIP: 0010:ark_set_pixclock drivers/video/fbdev/arkfb.c:504 [inline] RIP: 0010:arkfb_set_par+0x10fc/0x24c0 drivers/video/fbdev/arkfb.c:784 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 ark_set_pixclock() first. Fixes: 681e14730c73 ("arkfb: new framebuffer driver for ARK Logic cards") Signed-off-by: Zheyu Ma Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/arkfb.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/video/fbdev/arkfb.c b/drivers/video/fbdev/arkfb.c index 13ba371e70aa..bfa221b68d71 100644 --- a/drivers/video/fbdev/arkfb.c +++ b/drivers/video/fbdev/arkfb.c @@ -778,7 +778,12 @@ static int arkfb_set_par(struct fb_info *info) return -EINVAL; } =20 - ark_set_pixclock(info, (hdiv * info->var.pixclock) / hmul); + value =3D (hdiv * info->var.pixclock) / hmul; + if (!value) { + fb_dbg(info, "invalid pixclock\n"); + value =3D 1; + } + ark_set_pixclock(info, value); svga_set_timings(par->state.vgabase, &ark_timing_regs, &(info->var), hmul= , hdiv, (info->var.vmode & FB_VMODE_DOUBLE) ? 2 : 1, (info->var.vmode & FB_VMODE_INTERLACED) ? 2 : 1, --=20 2.35.1