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 9DDEEC46467 for ; Tue, 5 Apr 2022 10:08:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351027AbiDEKAx (ORCPT ); Tue, 5 Apr 2022 06:00:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234323AbiDEIYv (ORCPT ); Tue, 5 Apr 2022 04:24:51 -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 DA45213CE4; Tue, 5 Apr 2022 01:20:31 -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 76B2D60B12; Tue, 5 Apr 2022 08:20:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 813BDC385A0; Tue, 5 Apr 2022 08:20:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649146830; bh=xuNZMXifvmTGhpPgK2BkPkaKp82sCR/h9SV2ylyFzog=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aCPwRPIKA98xNCVygWgF08zf5KW/JXTyXJj+AgTBZpFdKCWUUyE5k6CU2vxDamCjB D00/advRjqD/PCi3yj7gRthsHY+OV6DmmdpfYA4zHOsjP8V0QJEdR6eJPLrJOCzE+7 o9JJJjaFqcyvHbiOWs7fACqBemEqXx/f6iah3+SI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, George Kennedy , Geert Uytterhoeven , Helge Deller , Sasha Levin Subject: [PATCH 5.17 0904/1126] video: fbdev: cirrusfb: check pixclock to avoid divide by zero Date: Tue, 5 Apr 2022 09:27:31 +0200 Message-Id: <20220405070434.064194492@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070407.513532867@linuxfoundation.org> References: <20220405070407.513532867@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: George Kennedy [ Upstream commit 5c6f402bdcf9e7239c6bc7087eda71ac99b31379 ] Do a sanity check on pixclock value to avoid divide by zero. If the pixclock value is zero, the cirrusfb driver will round up pixclock to get the derived frequency as close to maxclock as possible. Syzkaller reported a divide error in cirrusfb_check_pixclock. divide error: 0000 [#1] SMP KASAN PTI CPU: 0 PID: 14938 Comm: cirrusfb_test Not tainted 5.15.0-rc6 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2 RIP: 0010:cirrusfb_check_var+0x6f1/0x1260 Call Trace: fb_set_var+0x398/0xf90 do_fb_ioctl+0x4b8/0x6f0 fb_ioctl+0xeb/0x130 __x64_sys_ioctl+0x19d/0x220 do_syscall_64+0x3a/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae Signed-off-by: George Kennedy Reviewed-by: Geert Uytterhoeven Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/cirrusfb.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/video/fbdev/cirrusfb.c b/drivers/video/fbdev/cirrusfb.c index 93802abbbc72..3d47c347b897 100644 --- a/drivers/video/fbdev/cirrusfb.c +++ b/drivers/video/fbdev/cirrusfb.c @@ -469,7 +469,7 @@ static int cirrusfb_check_mclk(struct fb_info *info, long freq) return 0; } -static int cirrusfb_check_pixclock(const struct fb_var_screeninfo *var, +static int cirrusfb_check_pixclock(struct fb_var_screeninfo *var, struct fb_info *info) { long freq; @@ -478,9 +478,7 @@ static int cirrusfb_check_pixclock(const struct fb_var_screeninfo *var, unsigned maxclockidx = var->bits_per_pixel >> 3; /* convert from ps to kHz */ - freq = PICOS2KHZ(var->pixclock); - - dev_dbg(info->device, "desired pixclock: %ld kHz\n", freq); + freq = PICOS2KHZ(var->pixclock ? : 1); maxclock = cirrusfb_board_info[cinfo->btype].maxclock[maxclockidx]; cinfo->multiplexing = 0; @@ -488,11 +486,13 @@ static int cirrusfb_check_pixclock(const struct fb_var_screeninfo *var, /* If the frequency is greater than we can support, we might be able * to use multiplexing for the video mode */ if (freq > maxclock) { - dev_err(info->device, - "Frequency greater than maxclock (%ld kHz)\n", - maxclock); - return -EINVAL; + var->pixclock = KHZ2PICOS(maxclock); + + while ((freq = PICOS2KHZ(var->pixclock)) > maxclock) + var->pixclock++; } + dev_dbg(info->device, "desired pixclock: %ld kHz\n", freq); + /* * Additional constraint: 8bpp uses DAC clock doubling to allow maximum * pixel clock -- 2.34.1