From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765609AbdDSPbR (ORCPT ); Wed, 19 Apr 2017 11:31:17 -0400 Received: from mail.kernel.org ([198.145.29.136]:53530 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764451AbdDSOiP (ORCPT ); Wed, 19 Apr 2017 10:38:15 -0400 Date: Wed, 19 Apr 2017 23:37:50 +0900 From: Masami Hiramatsu To: "Naveen N. Rao" Cc: Michael Ellerman , Ingo Molnar , Ananth N Mavinakayanahalli , Masami Hiramatsu , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/7] kprobes: validate the symbol name length Message-Id: <20170419233750.8552f5de8ce1ed1398807284@kernel.org> In-Reply-To: <6e14d22994530fb5200c74d1593e73541d3b8028.1492604782.git.naveen.n.rao@linux.vnet.ibm.com> References: <6e14d22994530fb5200c74d1593e73541d3b8028.1492604782.git.naveen.n.rao@linux.vnet.ibm.com> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Apr 2017 18:21:02 +0530 "Naveen N. Rao" wrote: > When a kprobe is being registered, we use the symbol_name field to > lookup the address where the probe should be placed. Since this is a > user-provided field, let's ensure that the length of the string is > within expected limits. Would we really need this? Of course it may filter out longer strings... anyway such name should be rejected by kallsyms. [...] > 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) This just check the length of symbol_name buffer, and can contain some invalid chars. > +{ > + size_t sym_len; > + char *s; > + > + s = strchr(name, ':'); > + if (s) { > + sym_len = strnlen(s+1, KSYM_NAME_LEN); If you use strnlen() here, you just need to ensure sym_len < 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) Would you mean KSYM_NAME_LEN here? > + return false; > + } > + > + return true; > +} > + > /* > * If we have a symbol_name argument, look it up and add the offset field > * to it. This way, we can specify a relative address to a symbol. > @@ -1397,6 +1419,8 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p) > goto invalid; > > if (p->symbol_name) { > + if (!is_valid_kprobe_symbol_name(p->symbol_name)) > + return ERR_PTR(-EINVAL); > addr = kprobe_lookup_name(p->symbol_name, p->offset); > if (!addr) > return ERR_PTR(-ENOENT); > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 5f688cc724f0..bf73e5f31128 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -704,6 +704,10 @@ static int create_trace_kprobe(int argc, char **argv) > pr_info("Return probe must be used without offset.\n"); > return -EINVAL; > } > + if (!is_valid_kprobe_symbol_name(symbol)) { > + pr_info("Symbol name is too long.\n"); > + return -EINVAL; > + } > } > argc -= 2; argv += 2; > > -- > 2.12.1 > Thanks, -- Masami Hiramatsu