From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932166AbdJXJJY (ORCPT ); Tue, 24 Oct 2017 05:09:24 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:56426 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682AbdJXJJU (ORCPT ); Tue, 24 Oct 2017 05:09:20 -0400 Date: Tue, 24 Oct 2017 11:09:27 +0200 From: Greg KH To: Chen Feng Cc: zhaoyukun@huawei.com, tytso@mit.edu, arnd@arndb.de, linux-kernel@vger.kernel.org, suzhuangluan@hisilicon.com, dan.zhao@hisilicon.com Subject: Re: [PATCH RFC] random: fix syzkaller fuzzer test int overflow Message-ID: <20171024090927.GA20625@kroah.com> References: <1508831057-64195-1-git-send-email-puck.chen@hisilicon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1508831057-64195-1-git-send-email-puck.chen@hisilicon.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: > [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] > Restart is not permit > ================================================================= > UBSAN: Undefined behaviour in > kernel/linux-4.4/drivers/char/random.c:676:19 > signed integer overflow: > 2147483645 + 268435455 cannot be represented in type 'int' > CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 Does this also happen on 4.14-rc6? > TGID: 11928 Comm: syz-executor > Hardware name: hi3660 (DT) > Call trace: > [] dump_backtrace+0x0/0x314 > [] show_stack+0x1c/0x24 > [] dump_stack+0xdc/0x130 > [] ubsan_epilogue+0x18/0x6c > [] handle_overflow+0x180/0x1d4 > [] __ubsan_handle_add_overflow+0x2c/0x34 > [] credit_entropy_bits+0x358/0x9a8 > [] random_ioctl+0x338/0x384 > [] do_vfs_ioctl+0x60c/0xa4c > [] SyS_ioctl+0x9c/0xc0 > [] el0_svc_naked+0x24/0x28 > ================================================================= > > Signed-off-by: Chen Feng > Signed-off-by: Yukun Zhao > --- > drivers/char/random.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index 1ef2640..6f2bd6a 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -699,6 +699,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) > if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) > goto retry; > > + if (INT_MAX - nbits < r->entropy_total) { > + WARN_ON(1); Why WARN_ON()? What is that going to help with? thanks, greg k-h