From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753480AbcLHU3z (ORCPT ); Thu, 8 Dec 2016 15:29:55 -0500 Received: from mail-io0-f176.google.com ([209.85.223.176]:33630 "EHLO mail-io0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752035AbcLHU3w (ORCPT ); Thu, 8 Dec 2016 15:29:52 -0500 MIME-Version: 1.0 In-Reply-To: <20161208194824.2532-1-mcgrof@kernel.org> References: <20161208184801.1689-1-mcgrof@kernel.org> <20161208194824.2532-1-mcgrof@kernel.org> From: Kees Cook Date: Thu, 8 Dec 2016 12:29:42 -0800 X-Google-Sender-Auth: u2q1AEQ1UiYfQ0gUiwKGpHtMnj0 Message-ID: Subject: Re: [RFC 04/10] kmod: provide wrappers for kmod_concurrent inc/dec To: "Luis R. Rodriguez" Cc: shuah@kernel.org, Jessica Yu , Rusty Russell , "Eric W. Biederman" , Dmitry Torokhov , Arnaldo Carvalho de Melo , Jonathan Corbet , martin.wilck@suse.com, Michal Marek , Petr Mladek , hare@suse.com, rwright@hpe.com, Jeff Mahoney , DSterba@suse.com, fdmanana@suse.com, neilb@suse.com, Guenter Roeck , rgoldwyn@suse.com, subashab@codeaurora.org, Heinrich Schuchardt , Aaron Tomlin , mbenes@suse.cz, "Paul E. McKenney" , Dan Williams , Josh Poimboeuf , "David S. Miller" , Ingo Molnar , Andrew Morton , Linus Torvalds , linux-kselftest@vger.kernel.org, "linux-doc@vger.kernel.org" , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 8, 2016 at 11:48 AM, Luis R. Rodriguez wrote: > kmod_concurrent is used as an atomic counter for enabling > the allowed limit of modprobe calls, provide wrappers for it > to enable this to be expanded on more easily. This will be done > later. > > Signed-off-by: Luis R. Rodriguez > --- > kernel/kmod.c | 27 +++++++++++++++++++++------ > 1 file changed, 21 insertions(+), 6 deletions(-) > > diff --git a/kernel/kmod.c b/kernel/kmod.c > index cb6f7ca7b8a5..049d7eabda38 100644 > --- a/kernel/kmod.c > +++ b/kernel/kmod.c > @@ -44,6 +44,9 @@ > #include > > extern int max_threads; > + > +static atomic_t kmod_concurrent = ATOMIC_INIT(0); > + > unsigned int max_modprobes; > module_param(max_modprobes, uint, 0644); > MODULE_PARM_DESC(max_modprobes, "Max number of allowed concurrent modprobes"); > @@ -108,6 +111,20 @@ static int call_modprobe(char *module_name, int wait) > return -ENOMEM; > } > > +static int kmod_umh_threads_get(void) > +{ > + atomic_inc(&kmod_concurrent); > + if (atomic_read(&kmod_concurrent) < max_modprobes) > + return 0; > + atomic_dec(&kmod_concurrent); > + return -ENOMEM; > +} > + > +static void kmod_umh_threads_put(void) > +{ > + atomic_dec(&kmod_concurrent); > +} Can you use a kref here instead? We're trying to kill raw use of atomic_t for reference counting... > + > /** > * __request_module - try to load a kernel module > * @wait: wait (or not) for the operation to complete > @@ -129,7 +146,6 @@ int __request_module(bool wait, const char *fmt, ...) > va_list args; > char module_name[MODULE_NAME_LEN]; > int ret; > - static atomic_t kmod_concurrent = ATOMIC_INIT(0); > static int kmod_loop_msg; > > /* > @@ -153,8 +169,8 @@ int __request_module(bool wait, const char *fmt, ...) > if (ret) > return ret; > > - atomic_inc(&kmod_concurrent); > - if (atomic_read(&kmod_concurrent) > max_modprobes) { > + ret = kmod_umh_threads_get(); > + if (ret) { > /* We may be blaming an innocent here, but unlikely */ > if (kmod_loop_msg < 5) { > printk(KERN_ERR > @@ -162,15 +178,14 @@ int __request_module(bool wait, const char *fmt, ...) > module_name); > kmod_loop_msg++; > } > - atomic_dec(&kmod_concurrent); > - return -ENOMEM; > + return ret; > } > > trace_module_request(module_name, wait, _RET_IP_); > > ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC); > > - atomic_dec(&kmod_concurrent); > + kmod_umh_threads_put(); > return ret; > } > EXPORT_SYMBOL(__request_module); > -- > 2.10.1 > -- Kees Cook Nexus Security