Re: [BISECTED] 4943ba16 ("include crypto- module prefix") breaks wifi

[Kees Cook <keescook@chromium.org>]

On Thu, Apr 30, 2015 at 4:00 AM, George Spelvin <linux@horizon.com> wrote:
> Sorry for the long silence; the last e-mails arrived as I went on a trip,
> and the packet got lost.
>
> I just upgraded my laptop to 4.0.1 and had to remember the magic
> incantation to get the wireless working.  ("modprobe ctr")
>
>> George, any updates on this?
>
> It turns out that I found the problem.  An odd bit of pilot error, but
> NOT a kernel problem.  See bottom.
>
>> Also, could you please provide the output of "depmod -n | grep
>> crypto-"? There should be lines for crypto-ccm and crypto-ctr if you
>> build them as modules.
>
> alias crypto-twofish-asm twofish_i586
> alias crypto-twofish twofish_i586
> alias crypto-salsa20-asm salsa20_i586
> alias crypto-salsa20 salsa20_i586
> alias crypto-serpent serpent_sse2_i586
> alias crypto-cmac cmac
> alias crypto-xcbc xcbc
> alias crypto-md4 md4
> alias crypto-sha256-generic sha256_generic
> alias crypto-sha256 sha256_generic
> alias crypto-sha224-generic sha256_generic
> alias crypto-sha224 sha256_generic
> alias crypto-ecb ecb
> alias crypto-lrw lrw
> alias crypto-xts xts
> alias crypto-ctr ctr
> alias crypto-rfc3686 ctr
> alias crypto-gcm gcm
> alias crypto-rfc4543 gcm
> alias crypto-rfc4106 gcm
> alias crypto-gcm_base gcm
> alias crypto-ccm ccm
> alias crypto-rfc4309 ccm
> alias crypto-ccm_base ccm
> alias crypto-cryptd cryptd
> alias crypto-twofish-generic twofish_generic
> alias crypto-twofish twofish_generic
> alias crypto-serpent-generic serpent_generic
> alias crypto-serpent serpent_generic
> alias crypto-tnepres serpent_generic
> alias crypto-salsa20-generic salsa20_generic
> alias crypto-salsa20 salsa20_generic
> alias crypto-michael_mic michael_mic
> alias crypto-crc32 crc32
> alias crypto-ansi_cprng ansi_cprng
> alias crypto-stdrng ansi_cprng
> alias crypto-ghash-generic ghash_generic
> alias crypto-ghash ghash_generic
>
>
> Anyway, the problem was a long time ago, in /etc/modprobe.d/local.conf,
> I had blacklisted several unwanted crypto modules in order to suppress
> some mysterious urge my system had to load every loadable module at
> boot time.
>
> "Hey, bozo!  The point of making them modules is that I *don't* want them
> taking up unswappable memory all the time!"  So I hit it with a hammer.
>
> One line written years ago was "blacklist ctr".  The light dawns.
>
> It turns out that this doesn's stop an explicit "modprobe ctr" from
> working, but *does* stop alias processing that resolves to ctr.
> Thus, the kernel change broke my strange kmod (mis-)configuration.
>
> This fits the observed symptoms, and I apologize for wasting your time.

No worries! Thanks for digging into it. I was really scratching my head. :)

-Kees

-- 
Kees Cook
Chrome OS Security