From patchwork Tue Mar 19 12:20:03 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shile Zhang X-Patchwork-Id: 10859525 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5B00A1390 for ; Tue, 19 Mar 2019 12:21:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3C84B28FEE for ; Tue, 19 Mar 2019 12:21:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3068029550; Tue, 19 Mar 2019 12:21:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9102F294CE for ; Tue, 19 Mar 2019 12:21:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727442AbfCSMVL (ORCPT ); Tue, 19 Mar 2019 08:21:11 -0400 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:55923 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727386AbfCSMVL (ORCPT ); Tue, 19 Mar 2019 08:21:11 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R721e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07487;MF=shile.zhang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0TN7ZAKx_1552998045; Received: from e18g09479.et15sqa.tbsite.net(mailfrom:shile.zhang@linux.alibaba.com fp:SMTPD_---0TN7ZAKx_1552998045) by smtp.aliyun-inc.com(127.0.0.1); Tue, 19 Mar 2019 20:21:06 +0800 From: shile.zhang@linux.alibaba.com To: Bartlomiej Zolnierkiewicz , Fredrik Noring , Daniel Vetter Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, Shile Zhang Subject: [PATCH] fbdev: fix divide error in fb_var_to_videomode Date: Tue, 19 Mar 2019 20:20:03 +0800 Message-Id: <1552998003-237288-1-git-send-email-shile.zhang@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Shile Zhang 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 Reviewed-by: Mukesh Ojha --- drivers/video/fbdev/core/modedb.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/video/fbdev/core/modedb.c b/drivers/video/fbdev/core/modedb.c index 283d9307..ac04987 100644 --- 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_videomode *mode, if (var->vmode & FB_VMODE_DOUBLE) vtotal *= 2; + if (!htotal || !vtotal) + return; + hfreq = pixclock/htotal; mode->refresh = hfreq/vtotal; }