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 X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0956DC072B1 for ; Thu, 30 May 2019 04:59:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D717F26092 for ; Thu, 30 May 2019 04:59:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559192384; bh=/2LHEkYu/goeeY7c4o2zeiu0wluSLY7o9LR3wpTiklk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Z7O/7C0+LJIHfyPHn4QidLUfuCvXLxCpD4cE7brmsBMTh/F1lqRztF8tkNudDn77o YgNh3HJwouhknPDf9AZLvvFWzsumBKEwoE8XJUaXiKYzaHSC0vUOvTi0TDiDN5J3f7 E5cYF1sseMUCHOwNkVwt6osMJidBqzSg7QjRe41A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389355AbfE3E7n (ORCPT ); Thu, 30 May 2019 00:59:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:44662 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727657AbfE3DJg (ORCPT ); Wed, 29 May 2019 23:09:36 -0400 Received: from localhost (ip67-88-213-2.z213-88-67.customer.algx.net [67.88.213.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9BB4824488; Thu, 30 May 2019 03:09:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559185775; bh=/2LHEkYu/goeeY7c4o2zeiu0wluSLY7o9LR3wpTiklk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PWapk4ES6peUVIxT4HhIhXFuCpwkq9ifj1l+AxeXUCo3Y/JQUQo+p5Qawn+h7tErN UqhIEZFFk+jETKfdEtvH19c4Bd+B05OOb6lVsSDHuxMBgK0K+fm3u+ThCe60j0DqXf S8SWDbUU9rFTctzGXaY1e1uaKOMaFSCoe4A8S/ag= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Shile Zhang , Fredrik Noring , Daniel Vetter , Mukesh Ojha , Bartlomiej Zolnierkiewicz Subject: [PATCH 5.1 030/405] fbdev: fix divide error in fb_var_to_videomode Date: Wed, 29 May 2019 20:00:28 -0700 Message-Id: <20190530030542.231036206@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030540.291644921@linuxfoundation.org> References: <20190530030540.291644921@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Shile Zhang commit cf84807f6dd0be5214378e66460cfc9187f532f9 upstream. To fix following divide-by-zero error found by Syzkaller: divide error: 0000 [#1] SMP PTI CPU: 7 PID: 8447 Comm: test Kdump: loaded Not tainted 4.19.24-8.al7.x86_64 #1 Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014 RIP: 0010:fb_var_to_videomode+0xae/0xc0 Code: 04 44 03 46 78 03 4e 7c 44 03 46 68 03 4e 70 89 ce d1 ee 69 c0 e8 03 00 00 f6 c2 01 0f 45 ce 83 e2 02 8d 34 09 0f 45 ce 31 d2 <41> f7 f0 31 d2 f7 f1 89 47 08 f3 c3 66 0f 1f 44 00 00 0f 1f 44 00 RSP: 0018:ffffb7e189347bf0 EFLAGS: 00010246 RAX: 00000000e1692410 RBX: ffffb7e189347d60 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffb7e189347c10 RBP: ffff99972a091c00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000100 R13: 0000000000010000 R14: 00007ffd66baf6d0 R15: 0000000000000000 FS: 00007f2054d11740(0000) GS:ffff99972fbc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f205481fd20 CR3: 00000004288a0001 CR4: 00000000001606a0 Call Trace: fb_set_var+0x257/0x390 ? lookup_fast+0xbb/0x2b0 ? fb_open+0xc0/0x140 ? chrdev_open+0xa6/0x1a0 do_fb_ioctl+0x445/0x5a0 do_vfs_ioctl+0x92/0x5f0 ? __alloc_fd+0x3d/0x160 ksys_ioctl+0x60/0x90 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x5b/0x190 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f20548258d7 Code: 44 00 00 48 8b 05 b9 15 2d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 89 15 2d 00 f7 d8 64 89 01 48 It can be triggered easily with following test code: #include #include #include int main(void) { struct fb_var_screeninfo var = {.activate = 0x100, .pixclock = 60}; int fd = open("/dev/fb0", O_RDWR); if (fd < 0) return 1; if (ioctl(fd, FBIOPUT_VSCREENINFO, &var)) return 1; return 0; } Signed-off-by: Shile Zhang Cc: Fredrik Noring Cc: Daniel Vetter Reviewed-by: Mukesh Ojha Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/core/modedb.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/video/fbdev/core/modedb.c +++ b/drivers/video/fbdev/core/modedb.c @@ -935,6 +935,9 @@ void fb_var_to_videomode(struct fb_video if (var->vmode & FB_VMODE_DOUBLE) vtotal *= 2; + if (!htotal || !vtotal) + return; + hfreq = pixclock/htotal; mode->refresh = hfreq/vtotal; }