From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752175AbdJXJkq (ORCPT ); Tue, 24 Oct 2017 05:40:46 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:33493 "EHLO huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751604AbdJXJkm (ORCPT ); Tue, 24 Oct 2017 05:40:42 -0400 X-Greylist: delayed 966 seconds by postgrey-1.27 at vger.kernel.org; Tue, 24 Oct 2017 05:40:41 EDT Subject: Re: [PATCH RFC] random: fix syzkaller fuzzer test int overflow To: Greg KH References: <1508831057-64195-1-git-send-email-puck.chen@hisilicon.com> <20171024090927.GA20625@kroah.com> CC: , , , , , From: Chen Feng Message-ID: <59EF06B1.8020108@hisilicon.com> Date: Tue, 24 Oct 2017 17:24:01 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20171024090927.GA20625@kroah.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.142.193.64] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017/10/24 17:09, Greg KH wrote: > 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? No, mainline also has this issue. > >> 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? Actually, I am not familiar with the random module.... This patch is RFC to see if some one has better idea. -feng > > thanks, > > greg k-h > > . >