From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755329AbeDTPIj (ORCPT ); Fri, 20 Apr 2018 11:08:39 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:56606 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755295AbeDTPIh (ORCPT ); Fri, 20 Apr 2018 11:08:37 -0400 From: Ravi Bangoria To: rostedt@goodmis.org Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, jolsa@kernel.org, kamalesh@linux.vnet.ibm.com, Ravi Bangoria Subject: [RFC] trace_events: Fix kernel crash while using empty filter with perf Date: Fri, 20 Apr 2018 20:37:58 +0530 X-Mailer: git-send-email 2.14.3 X-TM-AS-GCONF: 00 x-cbid: 18042015-0008-0000-0000-000004ED83B4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18042015-0009-0000-0000-00001E819C46 Message-Id: <20180420150758.19787-1-ravi.bangoria@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-20_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-1804200152 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Kernel is crashing when user tries to record 'ftrace:function' event with empty filter: # perf record -e ftrace:function --filter="" ls # dmesg BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 Oops: 0000 [#1] SMP PTI ... RIP: 0010:ftrace_profile_set_filter+0x14b/0x2d0 RSP: 0018:ffffa4a7c0da7d20 EFLAGS: 00010246 RAX: ffffa4a7c0da7d64 RBX: 0000000000000000 RCX: 0000000000000006 RDX: 0000000000000000 RSI: 0000000000000092 RDI: ffff8c48ffc968f0 ... Call Trace: _perf_ioctl+0x54a/0x6b0 ? rcu_all_qs+0x5/0x30 ... After patch: # perf record -e ftrace:function --filter="" ls failed to set filter "" on event ftrace:function with 22 (Invalid argument) Also, if user tries to echo "" > filter, it used to throw an error. This behavior got changed by commit 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster"). This patch restores the behavior as a side effect: Before patch: # echo "" > filter # After patch: # echo "" > filter bash: echo: write error: Invalid argument # Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster") Signed-off-by: Ravi Bangoria --- kernel/trace/trace_events_filter.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 9b4716bb8bb0..1f951b3df60c 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1499,14 +1499,14 @@ static int process_preds(struct trace_event_call *call, return ret; } - if (!nr_preds) { - prog = NULL; - } else { - prog = predicate_parse(filter_string, nr_parens, nr_preds, + if (!nr_preds) + return -EINVAL; + + prog = predicate_parse(filter_string, nr_parens, nr_preds, parse_pred, call, pe); - if (IS_ERR(prog)) - return PTR_ERR(prog); - } + if (IS_ERR(prog)) + return PTR_ERR(prog); + rcu_assign_pointer(filter->prog, prog); return 0; } -- 2.14.3