From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Filipe Manana <fdmanana@suse.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
rgoldwyn@suse.com, hare <hare@suse.com>,
Jonathan Corbet <corbet@lwn.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kselftest@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Dan Williams <dan.j.williams@intel.com>,
Aaron Tomlin <atomlin@redhat.com>,
rwright@hpe.com, Heinrich Schuchardt <xypron.glpk@gmx.de>,
Michal Marek <mmarek@suse.com>,
martin.wilck@suse.com, Jeff Mahoney <jeffm@suse.com>,
Ingo Molnar <mingo@redhat.com>, Petr Mladek <pmladek@suse.com>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Guenter Roeck <linux@roeck-us.net>,
"Eric W. Biederman" <ebiederm@xmission.com>,
shuah@kernel.org, DSterba@suse.com,
Kees Cook <keescook@chromium.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Miroslav Benes <mbenes@suse.cz>, NeilBrown <neilb@suse.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
David Miller <davem@davemloft.net>, Jessica Yu <jeyu@redhat.com>,
Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
Julia Lawall <julia.lawall@lip6.fr>
Subject: Re: [RFC 10/10] kmod: add a sanity check on module loading
Date: Tue, 20 Dec 2016 12:52:06 -0600 [thread overview]
Message-ID: <CAB=NE6UgFir2u2UKUSqoxFYyuY9rQyJAvifBGi3QU1u15J=ihQ@mail.gmail.com> (raw)
In-Reply-To: <87fuljjua3.fsf@rustcorp.com.au>
On Mon, Dec 19, 2016 at 6:53 PM, Rusty Russell <rusty@rustcorp.com.au> wrote:
> Where does this NULL-deref is the module isn't correctly loaded?
No you are right, sorry -- I had confused a failure to mount over null
deref, my mistake.
>> *Iff* we want a sanity check to verify kmod's umh is not lying to us we
>> need to verify after 0 was returned that it was not lying to us. Since kmod
>> accepts aliases but find_modules_all() only works on the real module name a
>> validation check cannot happen when all you have are aliases.
>
> request_module() should block until resolution, but that's fundamentally
> a userspace problem. Let's not paper over it in kernelspace.
OK -- if userspace messes up again it may be a bit hard to prove
unless we have a validation debug thing in place, would such a thing
in debug form be reasonable ?
>> Yes; the kallsyms code does this on Oops. Not really a big issue in
>> practice, but a nice fix.
>>
>> Ok, will bundle into my queue.
>
> Please submit to Jessica for her module queue, as it's orthogonal
> AFAICT.
Will do.
>> I will note though that I still think there's a bug in this code --
>> upon a failure other "spinning" requests can fail, I believe this may
>> be due to not having another state or informing pending modules too
>> early of a failure but I haven't been able to prove this conjecture
>> yet.
>
> That's possible, but I can't see it from quickly re-checking the code.
>
> The module should be fully usable at this point; the module's init has
> been called successfully, so in the case of __get_fs_type() it should
> now succeed. The module cleans up its init section, but that should be
> independent.
>
> If there is a race, it's likely to be when some other caller wakes the
> queue. Moving the wakeup as soon as possible should make it easier to
> trigger:
>
> diff --git a/kernel/module.c b/kernel/module.c
> index f57dd63186e6..78bd89d41a22 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3397,6 +3397,7 @@ static noinline int do_init_module(struct module *mod)
>
> /* Now it's a first class citizen! */
> mod->state = MODULE_STATE_LIVE;
> + wake_up_all(&module_wq);
> blocking_notifier_call_chain(&module_notify_list,
> MODULE_STATE_LIVE, mod);
>
> @@ -3445,7 +3446,6 @@ static noinline int do_init_module(struct module *mod)
> */
> call_rcu_sched(&freeinit->rcu, do_free_init);
> mutex_unlock(&module_mutex);
> - wake_up_all(&module_wq);
>
> return 0;
>
Will give this a shot, thanks!
Luis
next prev parent reply other threads:[~2016-12-20 18:52 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-08 18:47 [RFC 00/10] kmod: stress test driver, few fixes and enhancements Luis R. Rodriguez
2016-12-08 18:47 ` [RFC 01/10] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2016-12-08 20:24 ` Kees Cook
2016-12-13 21:10 ` Luis R. Rodriguez
2016-12-16 7:41 ` Luis R. Rodriguez
2016-12-08 19:48 ` [RFC 02/10] module: fix memory leak on early load_module() failures Luis R. Rodriguez
2016-12-08 20:30 ` Kees Cook
2016-12-08 21:10 ` Luis R. Rodriguez
2016-12-08 21:17 ` Kees Cook
2016-12-09 17:06 ` Miroslav Benes
2016-12-16 8:51 ` Luis R. Rodriguez
2016-12-15 18:46 ` Aaron Tomlin
2016-12-08 19:48 ` [RFC 03/10] kmod: add dynamic max concurrent thread count Luis R. Rodriguez
2016-12-08 20:28 ` Kees Cook
2016-12-08 21:00 ` Luis R. Rodriguez
2016-12-14 15:38 ` Petr Mladek
2016-12-16 8:39 ` Luis R. Rodriguez
2017-01-10 19:24 ` Luis R. Rodriguez
2016-12-08 19:48 ` [RFC 04/10] kmod: provide wrappers for kmod_concurrent inc/dec Luis R. Rodriguez
2016-12-08 20:29 ` Kees Cook
2016-12-08 21:08 ` Luis R. Rodriguez
2016-12-15 12:46 ` Petr Mladek
2016-12-16 8:05 ` Luis R. Rodriguez
2016-12-22 4:48 ` Jessica Yu
2017-01-06 20:54 ` Luis R. Rodriguez
2017-01-10 18:57 ` [RFC 04/10] " Luis R. Rodriguez
2017-01-11 20:08 ` Luis R. Rodriguez
2017-05-16 18:02 ` Luis R. Rodriguez
2017-05-18 2:37 ` Luis R. Rodriguez
2016-12-22 5:07 ` Jessica Yu
2017-01-10 20:28 ` Luis R. Rodriguez
2016-12-08 19:48 ` [RFC 05/10] kmod: return -EBUSY if modprobe limit is reached Luis R. Rodriguez
2016-12-08 19:48 ` [RFC 06/10] kmod: provide sanity check on kmod_concurrent access Luis R. Rodriguez
2016-12-14 16:08 ` Petr Mladek
2016-12-14 17:12 ` Luis R. Rodriguez
2016-12-15 12:57 ` Petr Mladek
2017-01-10 20:00 ` Luis R. Rodriguez
2016-12-08 19:49 ` [RFC 07/10] kmod: use simplified rate limit printk Luis R. Rodriguez
2016-12-14 16:23 ` Petr Mladek
2016-12-14 16:41 ` Joe Perches
2016-12-16 8:44 ` Luis R. Rodriguez
2016-12-08 19:49 ` [RFC 08/10] sysctl: add support for unsigned int properly Luis R. Rodriguez
2016-12-08 19:49 ` [RFC 09/10] kmod: add helpers for getting kmod count and limit Luis R. Rodriguez
2016-12-15 16:56 ` Petr Mladek
2016-12-16 7:57 ` Luis R. Rodriguez
2017-01-11 18:27 ` Luis R. Rodriguez
2016-12-08 19:49 ` [RFC 10/10] kmod: add a sanity check on module loading Luis R. Rodriguez
2016-12-09 20:03 ` Martin Wilck
2016-12-09 20:56 ` Linus Torvalds
2016-12-15 18:08 ` Luis R. Rodriguez
2016-12-15 0:27 ` Rusty Russell
2016-12-16 8:31 ` Luis R. Rodriguez
2016-12-17 3:54 ` Rusty Russell
[not found] ` <CAB=NE6VvuA9a6hf6yoopGfUxVJQM5HyV5bNzUdsEtUV0UhbG-g@mail.gmail.com>
2016-12-20 0:53 ` Rusty Russell
2016-12-20 18:52 ` Luis R. Rodriguez [this message]
2016-12-21 2:21 ` Rusty Russell
2016-12-21 13:08 ` Luis R. Rodriguez
2017-01-03 0:04 ` Rusty Russell
2017-01-06 20:36 ` Luis R. Rodriguez
2017-01-06 21:53 ` Jessica Yu
2017-01-09 20:27 ` Luis R. Rodriguez
[not found] ` <87bmvgax51.fsf@rustcorp.com.au>
2017-01-09 19:56 ` [RFC 10/10] " Luis R. Rodriguez
2017-01-06 21:03 ` Jessica Yu
2017-01-04 2:47 ` Jessica Yu
2017-01-11 19:10 ` [RFC 00/10] kmod: stress test driver, few fixes and enhancements Luis R. Rodriguez
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