From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1040235AbdDUNyN (ORCPT ); Fri, 21 Apr 2017 09:54:13 -0400 Received: from mail.kernel.org ([198.145.29.136]:50718 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1040195AbdDUNyK (ORCPT ); Fri, 21 Apr 2017 09:54:10 -0400 Date: Fri, 21 Apr 2017 22:54:00 +0900 From: Masami Hiramatsu To: "Naveen N. Rao" Cc: Michael Ellerman , Ananth N Mavinakayanahalli , Ingo Molnar , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 3/7] kprobes: validate the symbol name provided during probe registration Message-Id: <20170421225400.81a4bd00f85725cf67c75e64@kernel.org> In-Reply-To: <20170421123234.6895-1-naveen.n.rao@linux.vnet.ibm.com> References: <6e14d22994530fb5200c74d1593e73541d3b8028.1492604782.git.naveen.n.rao@linux.vnet.ibm.com> <20170421123234.6895-1-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 Fri, 21 Apr 2017 18:02:33 +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. > > Signed-off-by: Naveen N. Rao > --- > Masami, Michael, > Here's a simplified version that should hopefully be fine. I have > simplified the logic to keep the code compact and simple. Ok, so as I replied to older version, - Ensure name != NULL at first. - Define it in kernel/kallsyms.c as a general routine. Since this validate the string which will be passed to kallsyms, I think it should be provided by kallsyms. Thanks, > > - Naveen > > > include/linux/kprobes.h | 1 + > kernel/kprobes.c | 30 ++++++++++++++++++++++++++++++ > kernel/trace/trace_kprobe.c | 4 ++++ > 3 files changed, 35 insertions(+) > > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h > index 1f82a3db00b1..4ee10fef5135 100644 > --- a/include/linux/kprobes.h > +++ b/include/linux/kprobes.h > @@ -405,6 +405,7 @@ int disable_kprobe(struct kprobe *kp); > int enable_kprobe(struct kprobe *kp); > > void dump_kprobe(struct kprobe *kp); > +bool is_valid_kprobe_symbol_name(const char *name); > > #else /* !CONFIG_KPROBES: */ > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 6a128f3a7ed1..ff9b1ac72a38 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1383,6 +1383,34 @@ bool within_kprobe_blacklist(unsigned long addr) > } > > /* > + * We mainly want to ensure that the provided string is of a reasonable length > + * and is of the form [:], so that this is safe to process > + * further. > + * We don't worry about invalid characters as those will just prevent > + * matching existing kallsyms. > + */ > +bool is_valid_kprobe_symbol_name(const char *name) > +{ > + size_t sym_len; > + const char *s; > + > + s = strnchr(name, ':', MODULE_NAME_LEN + KSYM_NAME_LEN + 1); > + if (s) { > + sym_len = (size_t)(s - name); > + if (sym_len <= 0 || sym_len >= MODULE_NAME_LEN) > + return false; > + s++; > + } else > + s = name; > + > + sym_len = strnlen(s, KSYM_NAME_LEN); > + if (sym_len <= 0 || sym_len >= KSYM_NAME_LEN) > + 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. > * This returns encoded errors if it fails to look up symbol or invalid > @@ -1397,6 +1425,8 @@ 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 > -- Masami Hiramatsu