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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 B8E42C0044C for ; Mon, 5 Nov 2018 16:37:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52C4820869 for ; Mon, 5 Nov 2018 16:37:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 52C4820869 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=alphalink.fr Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387608AbeKFB6L (ORCPT ); Mon, 5 Nov 2018 20:58:11 -0500 Received: from zimbra.alphalink.fr ([217.15.80.77]:45371 "EHLO zimbra.alphalink.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387420AbeKFB6K (ORCPT ); Mon, 5 Nov 2018 20:58:10 -0500 X-Greylist: delayed 378 seconds by postgrey-1.27 at vger.kernel.org; Mon, 05 Nov 2018 20:58:08 EST Received: from localhost (localhost [127.0.0.1]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id 68DEB2B52090; Mon, 5 Nov 2018 17:31:21 +0100 (CET) Received: from zimbra.alphalink.fr ([127.0.0.1]) by localhost (mail-2-cbv2.admin.alphalink.fr [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 41Etwg_CLTk3; Mon, 5 Nov 2018 17:31:19 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id 6DFBF2B52091; Mon, 5 Nov 2018 17:31:19 +0100 (CET) X-Virus-Scanned: amavisd-new at mail-2-cbv2.admin.alphalink.fr Received: from zimbra.alphalink.fr ([127.0.0.1]) by localhost (mail-2-cbv2.admin.alphalink.fr [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id L0N5hF5ixdnp; Mon, 5 Nov 2018 17:31:19 +0100 (CET) Received: from c-dev-0.admin.alphalink.fr (94-84-15-217.reverse.alphalink.fr [217.15.84.94]) by mail-2-cbv2.admin.alphalink.fr (Postfix) with ESMTP id 38F892B52090; Mon, 5 Nov 2018 17:31:19 +0100 (CET) Received: by c-dev-0.admin.alphalink.fr (Postfix, from userid 1000) id 0CAA2601CB; Mon, 5 Nov 2018 17:31:18 +0100 (CET) Date: Mon, 5 Nov 2018 17:31:18 +0100 From: Guillaume Nault To: Kyungtae Kim Cc: paulus@samba.org, davem@davemloft.net, Byoungyoung Lee , DaeRyong Jeong , syzkaller@googlegroups.com, netdev@vger.kernel.org, linux-ppp@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: UBSAN: Undefined behaviour in drivers/net/ppp/ppp_generic.c Message-ID: <20181105163118.GA1476@alphalink.fr> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 31, 2018 at 06:46:16AM -0400, Kyungtae Kim wrote: > We report a crash in v4.19-rc2 (and the latest kernel as well): > > kernel config: https://kt0755.github.io/etc/config_v2-4.19 > repro: https://kt0755.github.io/etc/repro.1e3e9.c > > unit_set() lacks the bounds checking for an integer variable n, > which causes integer overflow when it is equal to INT_MAX. > idr_alloc() does revert the overflowed n+1 to INT_MAX, so everything works as expected in practive. But sure, the code, as it is, looks wrong. > ======================================================= > UBSAN: Undefined behaviour in drivers/net/ppp/ppp_generic.c:3246:9 > signed integer overflow: > 2147483647 + 1 cannot be represented in type 'int' > CPU: 0 PID: 7676 Comm: syz-executor4 Not tainted 4.19.0-rc2 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0xd2/0x148 lib/dump_stack.c:113 > ubsan_epilogue+0x12/0x94 lib/ubsan.c:159 > handle_overflow+0x1cf/0x21a lib/ubsan.c:190 > __ubsan_handle_add_overflow+0x2a/0x31 lib/ubsan.c:198 > unit_set drivers/net/ppp/ppp_generic.c:3246 [inline] > ppp_unit_register drivers/net/ppp/ppp_generic.c:979 [inline] > ppp_dev_configure+0xbd8/0xd50 drivers/net/ppp/ppp_generic.c:1049 > ppp_create_interface drivers/net/ppp/ppp_generic.c:3013 [inline] > ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:848 [inline] > ppp_ioctl+0x1652/0x27f0 drivers/net/ppp/ppp_generic.c:601 > vfs_ioctl fs/ioctl.c:46 [inline] > do_vfs_ioctl+0x1c0/0x1150 fs/ioctl.c:687 > ksys_ioctl+0x9e/0xb0 fs/ioctl.c:702 > __do_sys_ioctl fs/ioctl.c:709 [inline] > __se_sys_ioctl fs/ioctl.c:707 [inline] > __x64_sys_ioctl+0x7e/0xc0 fs/ioctl.c:707 > do_syscall_64+0xc4/0x510 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4497b9 > Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 > 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d > 01 f0 ff ff 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f67b6f92c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00007f67b6f936cc RCX: 00000000004497b9 > RDX: 0000000020000080 RSI: 00000000c004743e RDI: 0000000000000013 > RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > R13: 0000000000005598 R14: 00000000006ed638 R15: 00007f67b6f93700 > ====================================================== > > A simple patch below is provided. > Note that in this control flow, negative n is already > filtered out (drivers/net/ppp/ppp_generic.c:965). > > --- a/drivers/net/ppp/ppp_generic.c > +++ b/drivers/net/ppp/ppp_generic.c > @@ -3243,6 +3243,9 @@ static int unit_set(struct idr *p, void *ptr, int n) > { > int unit; > > + if (n == INT_MAX) > + return -EINVAL; > + > unit = idr_alloc(p, ptr, n, n + 1, GFP_KERNEL); > if (unit == -ENOSPC) > unit = -EINVAL; > What about using idr_alloc_u32() instead? This way we could safely continue to accept INT_MAX, without relying on idr_alloc() internal safeguards.