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.o rg" <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: Wed, 21 Dec 2016 07:08:25 -0600 [thread overview]
Message-ID: <CAB=NE6Wd4jvUVS6pNds0yND_PX-MMpVjtvnJOHsNWX_5H7Mdkg@mail.gmail.com> (raw)
In-Reply-To: <87a8bqja3i.fsf@rustcorp.com.au>
On Tue, Dec 20, 2016 at 8:21 PM, Rusty Russell <rusty@rustcorp.com.au> wrote:
> "Luis R. Rodriguez" <mcgrof@kernel.org> writes:
>> 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 ?
>
> That makes perfect sense. Untested hack:
>
> diff --git a/fs/filesystems.c b/fs/filesystems.c
> index c5618db110be..e5c90e80c7d3 100644
> --- a/fs/filesystems.c
> +++ b/fs/filesystems.c
> @@ -275,9 +275,10 @@ struct file_system_type *get_fs_type(const char *name)
> int len = dot ? dot - name : strlen(name);
>
> fs = __get_fs_type(name, len);
> - if (!fs && (request_module("fs-%.*s", len, name) == 0))
> + if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
> fs = __get_fs_type(name, len);
> -
> + WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name);
> + }
> if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
> put_filesystem(fs);
> fs = NULL;
This is precisely a type of debug patch we had added first to verify "WTF".
> Maybe a similar hack for try_then_request_module(), but many places seem
> to open-code request_module() so it's not as trivial...
Right, out of ~350 request_module() calls (not included try requests)
only ~46 check the return value. Hence a validation check, and come to
think of it, *this* was the issue that originally had me believing
that in some places we might end up in a null deref --if those open
coded request_module() calls assume the driver is loaded there could
be many places where a NULL is inevitable. Granted, I agree they
should be fixed, we could add a grammar rule to start nagging at
driver developers for started, but it does beg the question also of
what a tightly knit validation for modprobe might look like, and hence
this patch and now the completed not-yet-posted alias work.
Would it be worthy as a kconfig kmod debugging aide for now? I can
follow up with a semantic patch to nag about checking the return value
of request_module(), and we can have 0-day then also complain about
new invalid uses.
Luis
next prev parent reply other threads:[~2016-12-21 13:08 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
2016-12-21 2:21 ` Rusty Russell
2016-12-21 13:08 ` Luis R. Rodriguez [this message]
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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