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Violators will be prosecuted; Wed, 18 Apr 2018 11:59:08 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w3IAx7Up45154516; Wed, 18 Apr 2018 10:59:07 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 86A9D4C050; Wed, 18 Apr 2018 11:51:37 +0100 (BST) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 68ACD4C052; Wed, 18 Apr 2018 11:51:36 +0100 (BST) Received: from localhost.localdomain (unknown [9.40.193.84]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 18 Apr 2018 11:51:36 +0100 (BST) From: Sandipan Das To: acme@kernel.org, jolsa@redhat.com Cc: linux-kernel@vger.kernel.org, naveen.n.rao@linux.vnet.ibm.com, ravi.bangoria@linux.vnet.ibm.com, sukadev@linux.vnet.ibm.com, maynard@us.ibm.com Subject: [PATCH v2 2/3] perf tools powerpc: Fix crash if callchain is empty Date: Wed, 18 Apr 2018 16:28:59 +0530 X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180418105900.5899-1-sandipan@linux.vnet.ibm.com> References: <20180418105900.5899-1-sandipan@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18041810-0012-0000-0000-000005CC2ECD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18041810-0013-0000-0000-000019487F66 Message-Id: <20180418105900.5899-3-sandipan@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-18_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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-1804180101 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For some cases, the callchain provided by the kernel may be empty. So, the callchain ip filtering code will cause a crash if we do not check whether the struct ip_callchain pointer is NULL before accessing any members. This can be observed on a powerpc64le system running Fedora 27 as shown below. # perf record -b -e cycles:u ls # perf report --branch-history perf: Segmentation fault -------- backtrace -------- perf[0x1027615c] linux-vdso64.so.1(__kernel_sigtramp_rt64+0x0)[0x7fff856304d8] perf(arch_skip_callchain_idx+0x44)[0x10257c58] perf[0x1017f2e4] perf(thread__resolve_callchain+0x124)[0x1017ff5c] perf(sample__resolve_callchain+0xf0)[0x10172788] ... Reported-by: Ravi Bangoria Signed-off-by: Sandipan Das --- tools/perf/arch/powerpc/util/skip-callchain-idx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c index d3a13f79d3ee..910db8762120 100644 --- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c +++ b/tools/perf/arch/powerpc/util/skip-callchain-idx.c @@ -262,7 +262,7 @@ int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain) int rc; u64 skip_slot = -1; - if (chain->nr < 3) + if (!chain || chain->nr < 3) return skip_slot; rc = check_return_addr(thread, chain->ips[1]); -- 2.14.3