From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964855AbdDTHVJ convert rfc822-to-8bit (ORCPT ); Thu, 20 Apr 2017 03:21:09 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37945 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S938610AbdDTHVF (ORCPT ); Thu, 20 Apr 2017 03:21:05 -0400 Date: Thu, 20 Apr 2017 07:19:28 +0000 From: "Naveen N. Rao" Subject: Re: [PATCH v3 3/7] kprobes: validate the symbol name length To: Ingo Molnar , Michael Ellerman Cc: Ananth N Mavinakayanahalli , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Masami Hiramatsu References: <6e14d22994530fb5200c74d1593e73541d3b8028.1492604782.git.naveen.n.rao@linux.vnet.ibm.com> <87o9vr4nm3.fsf@concordia.ellerman.id.au> In-Reply-To: <87o9vr4nm3.fsf@concordia.ellerman.id.au> User-Agent: astroid/0.8 (https://github.com/astroidmail/astroid) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT X-TM-AS-MML: disable x-cbid: 17042007-0016-0000-0000-0000022FEAB0 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17042007-0017-0000-0000-000006AAF2B8 Message-Id: <1492672015.e5bcoosx02.astroid@naverao1-tp.none> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-20_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1704200059 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Excerpts from Michael Ellerman's message of April 20, 2017 11:38: > "Naveen N. Rao" writes: > >> diff --git a/kernel/kprobes.c b/kernel/kprobes.c >> index 6a128f3a7ed1..bb86681c8a10 100644 >> --- a/kernel/kprobes.c >> +++ b/kernel/kprobes.c >> @@ -1382,6 +1382,28 @@ bool within_kprobe_blacklist(unsigned long addr) >> return false; >> } >> >> +bool is_valid_kprobe_symbol_name(const char *name) >> +{ >> + size_t sym_len; >> + char *s; >> + >> + s = strchr(name, ':'); >> + if (s) { >> + sym_len = strnlen(s+1, KSYM_NAME_LEN); >> + if (sym_len <= 0 || sym_len >= KSYM_NAME_LEN) >> + return false; >> + sym_len = (size_t)(s - name); >> + if (sym_len <= 0 || sym_len >= MODULE_NAME_LEN) >> + return false; >> + } else { >> + sym_len = strnlen(name, MODULE_NAME_LEN); >> + if (sym_len <= 0 || sym_len >= MODULE_NAME_LEN) >> + return false; >> + } > > I think this is probably more elaborate than it needs to be. > > Why not just check the string is <= (MODULE_NAME_LEN + KSYM_NAME_LEN) ? Yes, that would be sufficient for now. It's probably just me being paranoid, but I felt it's good to have stricter checks for user-provided strings, to guard against future changes to how we process this. - Naveen