From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932086AbcANBki (ORCPT ); Wed, 13 Jan 2016 20:40:38 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:46891 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752934AbcANBkT (ORCPT ); Wed, 13 Jan 2016 20:40:19 -0500 Subject: Re: [PATCH] locktorture: Fix NULL pointer when torture_type is invalid To: References: <1452650782-15099-1-git-send-email-wangkefeng.wang@huawei.com> <20160113162733.GO3818@linux.vnet.ibm.com> CC: Ingo Molnar , Peter Zijlstra , , From: Kefeng Wang Message-ID: <5696FBFC.40702@huawei.com> Date: Thu, 14 Jan 2016 09:38:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20160113162733.GO3818@linux.vnet.ibm.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.19.180] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.5696FC6F.0021,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 4729c1c6ff2b369c89a74d687cc2602a Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi paul, On 2016/1/14 0:27, Paul E. McKenney wrote: > On Wed, Jan 13, 2016 at 10:06:22AM +0800, Kefeng Wang wrote: >> Insmod locktorture with torture_type=mutex will lead to crash, >> >> Unable to handle kernel NULL pointer dereference at virtual address 00000008 >> pgd = ffffffc0f6c10000 >> [00000008] *pgd=000000013b221003, *pud=000000013b221003, *pmd=0000000000000000 >> Internal error: Oops: 94000006 [#1] PREEMPT SMP >> Modules linked in: locktorture(+) torture >> CPU: 2 PID: 1462 Comm: insmod Not tainted 4.4.0+ #19 >> Hardware name: linux,dummy-virt (DT) >> task: ffffffc0fb2b3700 ti: ffffffc0fa938000 task.ti: ffffffc0fa938000 >> PC is at __torture_print_stats+0x18/0x180 [locktorture] >> LR is at lock_torture_stats_print+0x68/0x110 [locktorture] >> pc : [] lr : [] pstate: 60000145 >> sp : ffffffc0fa93bb20 >> [snip...] >> Call trace: >> [] __torture_print_stats+0x18/0x180 [locktorture] >> [] lock_torture_stats_print+0x68/0x110 [locktorture] >> [] lock_torture_cleanup+0xc4/0x278 [locktorture] >> [] lock_torture_init+0x144/0x5b0 [locktorture] >> [] do_one_initcall+0x94/0x1a0 >> [] do_init_module+0x60/0x1c8 >> [] load_module+0x1880/0x1c9c >> [] SyS_finit_module+0x7c/0x88 >> [] el0_svc_naked+0x24/0x28 >> >> Fix it by check stats_task in lock_torture_cleanup() to guard not into >> a wrong path. >> >> Signed-off-by: Kefeng Wang > > Good catch! One question below... > >> --- >> kernel/locking/locktorture.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c >> index 8ef1919..1afa8ad 100644 >> --- a/kernel/locking/locktorture.c >> +++ b/kernel/locking/locktorture.c >> @@ -764,8 +764,10 @@ static void lock_torture_cleanup(void) >> reader_tasks = NULL; >> } >> >> - torture_stop_kthread(lock_torture_stats, stats_task); >> - lock_torture_stats_print(); /* -After- the stats thread is stopped! */ >> + if (stats_task) { >> + torture_stop_kthread(lock_torture_stats, stats_task); >> + lock_torture_stats_print(); /* -After- the stats thread is stopped! */ >> + } > > Does it work to have the following? > > + if (stats_task) > + torture_stop_kthread(lock_torture_stats, stats_task); > + lock_torture_stats_print(); /* -After- the stats thread is stopped! */ > > We need to print the statistics at the end of the run, even if we chose > not to print them periodically throughout the run. > No, the pc is in __torture_print_stats(char *page, struct lock_stress_stats *statp, bool write), that is 'long min = statp[0].n_lock_acquired;', if the torture_type is invalid, the statp is NULL, because the cxt.lwsa and cxt.lwsa/cxt.lrsa are not initialized in lock_torture_init(). Thanks, Kefeng > Thanx, Paul > >> if (atomic_read(&cxt.n_lock_torture_errors)) >> lock_torture_print_module_parms(cxt.cur_ops, >> -- >> 1.7.12.4 >> > > > . >