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 1C185ECAAD1 for ; Tue, 30 Aug 2022 17:27:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231686AbiH3R1C (ORCPT ); Tue, 30 Aug 2022 13:27:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231280AbiH3R0h (ORCPT ); Tue, 30 Aug 2022 13:26:37 -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 7E43C642C7; Tue, 30 Aug 2022 10:24:31 -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 37FA7617AE; Tue, 30 Aug 2022 17:24:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98E15C433C1; Tue, 30 Aug 2022 17:24:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661880263; bh=kUrZhZopLYc41rgNuZ0oBSix0hPLFs3SNFxYJUMGocM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=C2gFsWaCyaRlgyXBX8NhULU2axPou0+iqJUlz6FRSHvkVgrTOZ+Vy8nMaKP6IJuyg dkeS7DNoKETwuJGlaoUeXDcmsNV7EQBV1uAxw6zeU7kuEjdJV8nvuhThhAhF5+AqbW DGAEtJEoi8Wp6Oygy9sHdrSGiPkyiwpKywEtkdNIbBrflTaSrc4I5SUWFdLc/1m1kv HVV87yxFOr7V3/c1pJID/T9YUwsNCXSASCMHyVTBmTQN0lBfeW/TOiam6TTjys45Ps YdmpueP9VrjYUu3xgrAOV76RLMr3RvsKrS7jS4O+uzcImhLiItl3Vd+u3bQlDUPKrj gbjaHNbSgEdCg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Letu Ren , Zheyu Ma , Helge Deller , Sasha Levin , baihaowen@meizu.com, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: [PATCH AUTOSEL 5.10 14/16] fbdev: fb_pm2fb: Avoid potential divide by zero error Date: Tue, 30 Aug 2022 13:23:15 -0400 Message-Id: <20220830172317.581397-14-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220830172317.581397-1-sashal@kernel.org> References: <20220830172317.581397-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org From: Letu Ren [ Upstream commit 19f953e7435644b81332dd632ba1b2d80b1e37af ] In `do_fb_ioctl()` of fbmem.c, if cmd is FBIOPUT_VSCREENINFO, var will be copied from user, then go through `fb_set_var()` and `info->fbops->fb_check_var()` which could may be `pm2fb_check_var()`. Along the path, `var->pixclock` won't be modified. This function checks whether reciprocal of `var->pixclock` is too high. If `var->pixclock` is zero, there will be a divide by zero error. So, it is necessary to check whether denominator is zero to avoid crash. As this bug is found by Syzkaller, logs are listed below. divide error in pm2fb_check_var Call Trace: fb_set_var+0x367/0xeb0 drivers/video/fbdev/core/fbmem.c:1015 do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1110 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1189 Reported-by: Zheyu Ma Signed-off-by: Letu Ren Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/pm2fb.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/video/fbdev/pm2fb.c b/drivers/video/fbdev/pm2fb.c index 0642555289e06..c12d46e283598 100644 --- a/drivers/video/fbdev/pm2fb.c +++ b/drivers/video/fbdev/pm2fb.c @@ -616,6 +616,11 @@ static int pm2fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info) return -EINVAL; } + if (!var->pixclock) { + DPRINTK("pixclock is zero\n"); + return -EINVAL; + } + if (PICOS2KHZ(var->pixclock) > PM2_MAX_PIXCLOCK) { DPRINTK("pixclock too high (%ldKHz)\n", PICOS2KHZ(var->pixclock)); -- 2.35.1