From mboxrd@z Thu Jan 1 00:00:00 1970 From: mat Subject: Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel Date: Tue, 30 Nov 2010 22:20:25 +0100 Message-ID: <20101130222025.3ccf5c00@mat-laptop> References: <4CE2F914.9070106@free.fr> <20101129181542.GA11630@home.goodmis.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from smtp6-g21.free.fr ([212.27.42.6]:37721 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751222Ab0K3VUk convert rfc822-to-8bit (ORCPT ); Tue, 30 Nov 2010 16:20:40 -0500 In-Reply-To: <20101129181542.GA11630@home.goodmis.org> Sender: linux-next-owner@vger.kernel.org List-ID: To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-next@vger.kernel.org, Arjan van de Ven , James Morris , Andrew Morton , Andi Kleen , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar , Rusty Russell , Stephen Rothwell , Dave Jones , Siarhei Liakh , Kees Cook , Peter Zijlstra Hi, Le Mon, 29 Nov 2010 13:15:42 -0500, Steven Rostedt a =E9crit : > This patch breaks function tracer: >=20 > ------------[ cut here ]------------ > WARNING: at kernel/trace/ftrace.c:1014 ftrace_bug+0x114/0x171() > Hardware name: Precision WorkStation 470 =20 > Modules linked in: i2c_core(+) > Pid: 86, comm: modprobe Not tainted 2.6.37-rc2+ #68 > Call Trace: > [] warn_slowpath_common+0x85/0x9d > [] ? __process_new_adapter+0x7/0x34 [i2c_core] > [] ? __process_new_adapter+0x7/0x34 [i2c_core] > [] warn_slowpath_null+0x1a/0x1c > [] ftrace_bug+0x114/0x171 > [] ? __process_new_adapter+0x7/0x34 [i2c_core] > [] ftrace_process_locs+0x1ae/0x274 > [] ? __process_new_adapter+0x7/0x34 [i2c_core] > [] ftrace_module_notify+0x39/0x44 > [] notifier_call_chain+0x37/0x63 > [] __blocking_notifier_call_chain+0x46/0x5b > [] blocking_notifier_call_chain+0x14/0x16 > [] sys_init_module+0x73/0x1f3 > [] system_call_fastpath+0x16/0x1b > ---[ end trace 2aff4f4ca53ec746 ]--- > ftrace faulted on writing [] > __process_new_adapter+0x7/0x34 [i2c_core] >=20 >=20 > On Tue, Nov 16, 2010 at 10:35:16PM +0100, matthieu castet wrote: > > =20 > > @@ -2650,6 +2810,18 @@ static struct module *load_module(void > > __user *umod, kfree(info.strmap); > > free_copy(&info); > > =20 > > + /* Set RO and NX regions for core */ > > + set_section_ro_nx(mod->module_core, > > + mod->core_text_size, > > + mod->core_ro_size, > > + mod->core_size); > > + > > + /* Set RO and NX regions for init */ > > + set_section_ro_nx(mod->module_init, > > + mod->init_text_size, > > + mod->init_ro_size, > > + mod->init_size); > > + >=20 > Here we set the text read only before we call the notifiers. The > function tracer changes the calls to mcount into nops via a notifier > call so this must be done after the module notifiers. >=20 > > /* Done! */ > > trace_module_load(mod); > > return mod; > > @@ -2753,6 +2925,7 @@ SYSCALL_DEFINE3(init_module, void __user *, > > umod, mod->symtab =3D mod->core_symtab; > > mod->strtab =3D mod->core_strtab; > > #endif > > + unset_section_ro_nx(mod, mod->module_init); > > module_free(mod, mod->module_init); > > mod->module_init =3D NULL; > > mod->init_size =3D 0; >=20 > Below is the patch that fixes this bug. >=20 > -- Steve >=20 > Reported-by: Peter Zijlstra > Signed-off-by: Steven Rostedt >=20 > diff --git a/kernel/module.c b/kernel/module.c > index ba421e6..5ccf52c 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -2804,18 +2804,6 @@ static struct module *load_module(void __user > *umod, kfree(info.strmap); > free_copy(&info); > =20 > - /* Set RO and NX regions for core */ > - set_section_ro_nx(mod->module_core, > - mod->core_text_size, > - mod->core_ro_size, > - mod->core_size); > - > - /* Set RO and NX regions for init */ > - set_section_ro_nx(mod->module_init, > - mod->init_text_size, > - mod->init_ro_size, > - mod->init_size); > - > /* Done! */ > trace_module_load(mod); > return mod; > @@ -2876,6 +2864,18 @@ SYSCALL_DEFINE3(init_module, void __user *, > umod, blocking_notifier_call_chain(&module_notify_list, > MODULE_STATE_COMING, mod); > =20 > + /* Set RO and NX regions for core */ > + set_section_ro_nx(mod->module_core, > + mod->core_text_size, > + mod->core_ro_size, > + mod->core_size); > + > + /* Set RO and NX regions for init */ > + set_section_ro_nx(mod->module_init, > + mod->init_text_size, > + mod->init_ro_size, > + mod->init_size); > + > do_mod_ctors(mod); > /* Start the module */ > if (mod->init !=3D NULL) >=20 >=20 That's look fine for me. But I wonder why ftrace_arch_code_modify_prepare isn't called ? It is only called when we start/stop tracing ? Matthieu