From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751948AbeBZWCX (ORCPT ); Mon, 26 Feb 2018 17:02:23 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:34348 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751742AbeBZWCV (ORCPT ); Mon, 26 Feb 2018 17:02:21 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 03/12] rcutorture: Avoid fake-writer use of undefined primitives Date: Mon, 26 Feb 2018 14:02:32 -0800 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20180226220225.GA32136@linux.vnet.ibm.com> References: <20180226220225.GA32136@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18022622-0008-0000-0000-000002DB9DD3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008601; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000254; SDB=6.00995533; UDB=6.00506035; IPR=6.00774861; MB=3.00019751; MTD=3.00000008; XFM=3.00000015; UTC=2018-02-26 22:02:18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18022622-0009-0000-0000-00003864E98C Message-Id: <1519682561-510-3-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-26_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1802260276 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently the rcu_torture_fakewriter() function invokes cur_ops->sync() and cur_ops->exp_sync() without first checking to see if they are in fact non-NULL. This results in kernel NULL pointer dereferences when testing RCU implementations that choose not to provide the full set of primitives. Given that it is perfectly reasonable to have specialized RCU implementations that provide only a subset of the RCU API, this is a bug in rcutorture. This commit therefore makes rcu_torture_fakewriter() check function pointers before invoking them, thus allowing it to test subsetted RCU implementations. Reported-by: Lihao Liang Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 0f94025c672a..6c46cd1d8fd7 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1045,13 +1045,13 @@ rcu_torture_fakewriter(void *arg) torture_random(&rand) % (nfakewriters * 8) == 0) { cur_ops->cb_barrier(); } else if (gp_normal == gp_exp) { - if (torture_random(&rand) & 0x80) + if (cur_ops->sync && torture_random(&rand) & 0x80) cur_ops->sync(); - else + else if (cur_ops->exp_sync) cur_ops->exp_sync(); - } else if (gp_normal) { + } else if (gp_normal && cur_ops->sync) { cur_ops->sync(); - } else { + } else if (cur_ops->exp_sync) { cur_ops->exp_sync(); } stutter_wait("rcu_torture_fakewriter"); -- 2.5.2