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Message-ID: <20130121201221.GA8149@kroah.com>
Date: Mon, 21 Jan 2013 12:12:21 -0800
From: Greg KH <gregkh@...uxfoundation.org>
To: Rusty Russell <rusty@...tcorp.com.au>,
Prarit Bhargava <prarit@...hat.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
stable@...r.kernel.org
Subject: Re: module: put modules in list much earlier.
Rusty, should the commit below be applied to the 3.7-stable kernel tree?
thanks,
greg k-h
On Mon, Jan 21, 2013 at 01:46:13AM +0000, Linux Kernel Mailing List wrote:
> Gitweb: http://git.kernel.org/linus/;a=commit;h=1fb9341ac34825aa40354e74d9a2c69df7d2c304
> Commit: 1fb9341ac34825aa40354e74d9a2c69df7d2c304
> Parent: 0d21b0e3477395e7ff2acc269f15df6e6a8d356d
> Author: Rusty Russell <rusty@...tcorp.com.au>
> AuthorDate: Sat Jan 12 13:27:34 2013 +1030
> Committer: Rusty Russell <rusty@...tcorp.com.au>
> CommitDate: Sat Jan 12 13:27:46 2013 +1030
>
> module: put modules in list much earlier.
>
> Prarit's excellent bug report:
> > In recent Fedora releases (F17 & F18) some users have reported seeing
> > messages similar to
> >
> > [ 15.478160] kvm: Could not allocate 304 bytes percpu data
> > [ 15.478174] PERCPU: allocation failed, size=304 align=32, alloc from
> > reserved chunk failed
> >
> > during system boot. In some cases, users have also reported seeing this
> > message along with a failed load of other modules.
> >
> > What is happening is systemd is loading an instance of the kvm module for
> > each cpu found (see commit e9bda3b). When the module load occurs the kernel
> > currently allocates the modules percpu data area prior to checking to see
> > if the module is already loaded or is in the process of being loaded. If
> > the module is already loaded, or finishes load, the module loading code
> > releases the current instance's module's percpu data.
>
> Now we have a new state MODULE_STATE_UNFORMED, we can insert the
> module into the list (and thus guarantee its uniqueness) before we
> allocate the per-cpu region.
>
> Reported-by: Prarit Bhargava <prarit@...hat.com>
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> Tested-by: Prarit Bhargava <prarit@...hat.com>
> ---
> kernel/module.c | 90 ++++++++++++++++++++++++++++++-------------------------
> lib/bug.c | 1 +
> 2 files changed, 50 insertions(+), 41 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index c3a2ee8..ec535aa 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3017,7 +3017,7 @@ static bool finished_loading(const char *name)
> bool ret;
>
> mutex_lock(&module_mutex);
> - mod = find_module(name);
> + mod = find_module_all(name, true);
> ret = !mod || mod->state == MODULE_STATE_LIVE
> || mod->state == MODULE_STATE_GOING;
> mutex_unlock(&module_mutex);
> @@ -3141,6 +3141,32 @@ static int load_module(struct load_info *info, const char __user *uargs,
> goto free_copy;
> }
>
> + /*
> + * We try to place it in the list now to make sure it's unique
> + * before we dedicate too many resources. In particular,
> + * temporary percpu memory exhaustion.
> + */
> + mod->state = MODULE_STATE_UNFORMED;
> +again:
> + mutex_lock(&module_mutex);
> + if ((old = find_module_all(mod->name, true)) != NULL) {
> + if (old->state == MODULE_STATE_COMING
> + || old->state == MODULE_STATE_UNFORMED) {
> + /* Wait in case it fails to load. */
> + mutex_unlock(&module_mutex);
> + err = wait_event_interruptible(module_wq,
> + finished_loading(mod->name));
> + if (err)
> + goto free_module;
> + goto again;
> + }
> + err = -EEXIST;
> + mutex_unlock(&module_mutex);
> + goto free_module;
> + }
> + list_add_rcu(&mod->list, &modules);
> + mutex_unlock(&module_mutex);
> +
> #ifdef CONFIG_MODULE_SIG
> mod->sig_ok = info->sig_ok;
> if (!mod->sig_ok)
> @@ -3150,7 +3176,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
> /* Now module is in final location, initialize linked lists, etc. */
> err = module_unload_init(mod);
> if (err)
> - goto free_module;
> + goto unlink_mod;
>
> /* Now we've got everything in the final locations, we can
> * find optional sections. */
> @@ -3185,54 +3211,33 @@ static int load_module(struct load_info *info, const char __user *uargs,
> goto free_arch_cleanup;
> }
>
> - /* Mark state as coming so strong_try_module_get() ignores us. */
> - mod->state = MODULE_STATE_COMING;
> -
> - /* Now sew it into the lists so we can get lockdep and oops
> - * info during argument parsing. No one should access us, since
> - * strong_try_module_get() will fail.
> - * lockdep/oops can run asynchronous, so use the RCU list insertion
> - * function to insert in a way safe to concurrent readers.
> - * The mutex protects against concurrent writers.
> - */
> -again:
> - mutex_lock(&module_mutex);
> - if ((old = find_module(mod->name)) != NULL) {
> - if (old->state == MODULE_STATE_COMING) {
> - /* Wait in case it fails to load. */
> - mutex_unlock(&module_mutex);
> - err = wait_event_interruptible(module_wq,
> - finished_loading(mod->name));
> - if (err)
> - goto free_arch_cleanup;
> - goto again;
> - }
> - err = -EEXIST;
> - goto unlock;
> - }
> -
> - /* This has to be done once we're sure module name is unique. */
> dynamic_debug_setup(info->debug, info->num_debug);
>
> - /* Find duplicate symbols */
> + mutex_lock(&module_mutex);
> + /* Find duplicate symbols (must be called under lock). */
> err = verify_export_symbols(mod);
> if (err < 0)
> - goto ddebug;
> + goto ddebug_cleanup;
>
> + /* This relies on module_mutex for list integrity. */
> module_bug_finalize(info->hdr, info->sechdrs, mod);
> - list_add_rcu(&mod->list, &modules);
> +
> + /* Mark state as coming so strong_try_module_get() ignores us,
> + * but kallsyms etc. can see us. */
> + mod->state = MODULE_STATE_COMING;
> +
> mutex_unlock(&module_mutex);
>
> /* Module is ready to execute: parsing args may do that. */
> err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
> -32768, 32767, &ddebug_dyndbg_module_param_cb);
> if (err < 0)
> - goto unlink;
> + goto bug_cleanup;
>
> /* Link in to syfs. */
> err = mod_sysfs_setup(mod, info, mod->kp, mod->num_kp);
> if (err < 0)
> - goto unlink;
> + goto bug_cleanup;
>
> /* Get rid of temporary copy. */
> free_copy(info);
> @@ -3242,16 +3247,13 @@ again:
>
> return do_init_module(mod);
>
> - unlink:
> + bug_cleanup:
> + /* module_bug_cleanup needs module_mutex protection */
> mutex_lock(&module_mutex);
> - /* Unlink carefully: kallsyms could be walking list. */
> - list_del_rcu(&mod->list);
> module_bug_cleanup(mod);
> - wake_up_all(&module_wq);
> - ddebug:
> - dynamic_debug_remove(info->debug);
> - unlock:
> mutex_unlock(&module_mutex);
> + ddebug_cleanup:
> + dynamic_debug_remove(info->debug);
> synchronize_sched();
> kfree(mod->args);
> free_arch_cleanup:
> @@ -3260,6 +3262,12 @@ again:
> free_modinfo(mod);
> free_unload:
> module_unload_free(mod);
> + unlink_mod:
> + mutex_lock(&module_mutex);
> + /* Unlink carefully: kallsyms could be walking list. */
> + list_del_rcu(&mod->list);
> + wake_up_all(&module_wq);
> + mutex_unlock(&module_mutex);
> free_module:
> module_deallocate(mod, info);
> free_copy:
> diff --git a/lib/bug.c b/lib/bug.c
> index a28c141..d0cdf14 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -55,6 +55,7 @@ static inline unsigned long bug_addr(const struct bug_entry *bug)
> }
>
> #ifdef CONFIG_MODULES
> +/* Updates are protected by module mutex */
> static LIST_HEAD(module_bug_list);
>
> static const struct bug_entry *module_find_bug(unsigned long bugaddr)
> --
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