Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932337Ab1D1KIY (ORCPT ); Thu, 28 Apr 2011 06:08:24 -0400 Received: from mtagate7.uk.ibm.com ([194.196.100.167]:35795 "EHLO mtagate7.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752621Ab1D1KIX (ORCPT ); Thu, 28 Apr 2011 06:08:23 -0400 Subject: Re: Undoing module RONX protection fix From: Jan Glauber To: Rusty Russell Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, castet.matthieu@free.fr, sliakh.lkml@gmail.com, jiang@cs.ncsu.edu, mingo@elte.hu In-Reply-To: <87ipu0l1kt.fsf@rustcorp.com.au> References: <20110418092348.GB7786@hal> <20110418092801.GC3837@infradead.org> <874o5v6drb.fsf@rustcorp.com.au> <20110421141949.GA10675@hal> <87ipu0l1kt.fsf@rustcorp.com.au> Content-Type: text/plain; charset="UTF-8" Date: Thu, 28 Apr 2011 12:08:20 +0200 Message-ID: <1303985300.3495.93.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5646 Lines: 150 On Wed, 2011-04-27 at 14:42 +0930, Rusty Russell wrote: > On Thu, 21 Apr 2011 16:19:49 +0200, Jan Glauber wrote: > > On Mon, Apr 18, 2011 at 08:13:36PM +0930, Rusty Russell wrote: > > > On Mon, 18 Apr 2011 11:23:48 +0200, Jan Glauber wrote: > > > > While debugging I stumbled over two problems in the code that protects module > > > > pages. > > > > > > > > First issue is that disabling the protection before freeing init or unload of > > > > a module is not symmetric with the enablement. For instance, if pages are set > > > > to RO the page range from module_core to module_core + core_ro_size is > > > > protected. If a module is unloaded the page range from module_core to > > > > module_core + core_size is set back to RW. > > > > So pages that were not set to RO are also changed to RW. > > > > This is not critical but IMHO it should be symmetric. > > > > > > > > Second issue is that while set_memory_rw & set_memory_ro are used for > > > > RO/RW changes only set_memory_nx is involved for NX/X. One would await that > > > > the inverse function is called when the NX protection should be removed, > > > > which is not the case here, unless I'm missing something. > > > > > > > > The following patch addresses both issues. Works on s390. Boot tested on x86. > > > > > > > > Please comment, > > > > > > Applied, minus the S/390 EXPORT_SYMBOL which Christoph pointed out. I > > > turned your mail into the commit message, since it was clearer and more > > > verbose. I don't see why they would be different. > > > > There's a bug in my patch which just killed one of my s390 machines. > > Can you merge this with the previuos patch? > > Hmm... > > Applied, but that function is really kind of silly. We should probably > just split into unset_section_ro_nx() into unset_module_init_ro_nx() and > unset_module_core_ro_nx(). > > (And why isn't that function static anyway?) > > Patch appreciated :) > Rusty. How about this? To be honest I don't like the inverse naming like in unset no-execute too much, it makes me feel dizzy. But I wanted to keep the changes minimal. Jan ------ Split the unprotect function into a function per section to make the code more readable and add the missing static declaration. Signed-off-by: Jan Glauber --- kernel/module.c | 47 ++++++++++++++++++++++++++--------------------- 1 file changed, 26 insertions(+), 21 deletions(-) --- a/kernel/module.c +++ b/kernel/module.c @@ -1607,24 +1607,28 @@ static void set_section_ro_nx(void *base } } -/* Setting memory back to W+X before releasing it */ -void unset_section_ro_nx(struct module *mod, void *module_region) +static void unset_module_core_ro_nx(struct module *mod) { - if (mod->module_core && mod->module_core == module_region) { - set_page_attributes(mod->module_core + mod->core_text_size, - mod->module_core + mod->core_size, - set_memory_x); - set_page_attributes(mod->module_core, - mod->module_core + mod->core_ro_size, - set_memory_rw); - } else if (mod->module_init && mod->module_init == module_region) { - set_page_attributes(mod->module_init + mod->init_text_size, - mod->module_init + mod->init_size, - set_memory_x); - set_page_attributes(mod->module_init, - mod->module_init + mod->init_ro_size, - set_memory_rw); - } + if (mod->module_core == NULL) + return; + set_page_attributes(mod->module_core + mod->core_text_size, + mod->module_core + mod->core_size, + set_memory_x); + set_page_attributes(mod->module_core, + mod->module_core + mod->core_ro_size, + set_memory_rw); +} + +static void unset_module_init_ro_nx(struct module *mod) +{ + if (mod->module_init == NULL) + return; + set_page_attributes(mod->module_init + mod->init_text_size, + mod->module_init + mod->init_size, + set_memory_x); + set_page_attributes(mod->module_init, + mod->module_init + mod->init_ro_size, + set_memory_rw); } /* Iterate through all modules and set each module's text as RW */ @@ -1670,7 +1674,8 @@ void set_all_modules_text_ro() } #else static inline void set_section_ro_nx(void *base, unsigned long text_size, unsigned long ro_size, unsigned long total_size) { } -static inline void unset_section_ro_nx(struct module *mod, void *module_region) { } +static void unset_module_core_ro_nx(struct module *mod) { } +static void unset_module_init_ro_nx(struct module *mod) { } #endif /* Free a module, remove from lists, etc. */ @@ -1697,7 +1702,7 @@ static void free_module(struct module *m destroy_params(mod->kp, mod->num_kp); /* This may be NULL, but that's OK */ - unset_section_ro_nx(mod, mod->module_init); + unset_module_init_ro_nx(mod); module_free(mod, mod->module_init); kfree(mod->args); percpu_modfree(mod); @@ -1706,7 +1711,7 @@ static void free_module(struct module *m lockdep_free_key_range(mod->module_core, mod->core_size); /* Finally, free the core (containing the module structure) */ - unset_section_ro_nx(mod, mod->module_core); + unset_module_core_ro_nx(mod); module_free(mod, mod->module_core); #ifdef CONFIG_MPU @@ -2932,7 +2937,7 @@ SYSCALL_DEFINE3(init_module, void __user mod->symtab = mod->core_symtab; mod->strtab = mod->core_strtab; #endif - unset_section_ro_nx(mod, mod->module_init); + unset_module_init_ro_nx(mod); module_free(mod, mod->module_init); mod->module_init = NULL; mod->init_size = 0; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/