linux-kernel - Re: [security] d3b04a4398: WARNING:at_crypto/kdf_sp800108.c:#crypto_kdf108

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Date:   Fri, 10 Dec 2021 10:54:32 +0800
From:   Yujie Liu <yujie.liu@...el.com>
To:     Stephan Müller <smueller@...onox.de>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        <lkp@...ts.01.org>, <lkp@...el.com>,
        "Sang, Oliver" <oliver.sang@...el.com>
Subject: Re: [security] d3b04a4398:
 WARNING:at_crypto/kdf_sp800108.c:#crypto_kdf108_init

Hi Stephan,

On 12/5/2021 6:21 PM, Stephan Müller wrote:
> Am Dienstag, 30. November 2021, 09:04:19 CET schrieb kernel test robot:
> 
> Hi,
> 
> ...
>>
>>
>> +------------------------------------------------------+------------+-------
>> -----+
>> |                                                      | d792134423 |
>> |                                                      | d3b04a4398 |
>>
>> +------------------------------------------------------+------------+-------
>> -----+
>> | boot_successes                                       | 14         | 0
>> |     | boot_failures                                        | 0          |
>> | 16         | WARNING:at_crypto/kdf_sp800108.c:#crypto_kdf108_init | 0
>> |      | 16         | EIP:crypto_kdf108_init
>> | | 0          | 16         |
>> +------------------------------------------------------+------------+-------
>> -----+
>>
>>
>> If you fix the issue, kindly add following tag
>> Reported-by: kernel test robot <oliver.sang@...el.com>
>>
>>
>> [ 18.648980][ T1] WARNING: CPU: 0 PID: 1 at crypto/kdf_sp800108.c:138
>> crypto_kdf108_init (crypto/kdf_sp800108.c:136) [   18.649900][    T1]
>> Modules linked in:
> 
> The issue is that the self-test fails for 16 out of 30 times, i.e. it is kind
> of random when it happens or not.

+------------------------------------------------------+------------+------------+
|                                                      | d792134423 | d3b04a4398 |
+------------------------------------------------------+------------+------------+
| boot_successes                                       | 14         | 0          |
| boot_failures                                        | 0          | 16         |
| WARNING:at_crypto/kdf_sp800108.c:#crypto_kdf108_init | 0          | 16         |
| EIP:crypto_kdf108_init                               | 0          | 16         |
+------------------------------------------------------+------------+------------+

This table shows that we have tested commit d3b04a4398("security: DH - use KDF
implementation from crypto API") for several runs of boot test in qemu but got
100% bad result. We have also tested its parent commit (i.e. commit d792134423
"security: DH - remove dead code for zero padding") and all the runs got 100%
good result. So this is not a random issue.

> 
> I am unable to reproduce it with i386 and clang-13. I can also not reproduce
> it with GCC.

We have tested the i386 kernel built by gcc-9 or clang-14, and confirmed both
of them can reproduce this issue reliably.

Please be sure to follow the reproduce steps in original report mail. The full
reproduce log is attached.

> 
> Nor do I see an obvious issue in the code that points to either uninitizlized
> memory or otherwise could affect the test result.

the dmesg warning introduced by commit d3b04a4398 is:

[   11.061347][    T1] alg: kdf: could not allocate hash handle for hmac(sha256)
[   11.061744][    T1] ------------[ cut here ]------------
[   11.062032][    T1] alg: self-tests for CTR-KDF (hmac(sha256)) failed (rc=-12)
[   11.062454][    T1] WARNING: CPU: 0 PID: 1 at crypto/kdf_sp800108.c:136 crypto_kdf108_init+0xec/0x107
[   11.062959][    T1] Modules linked in:
[   11.063164][    T1] CPU: 0 PID: 1 Comm: swapper Not tainted 5.16.0-rc1-13186-gd3b04a4398fe #1
[   11.063624][    T1] EIP: crypto_kdf108_init+0xec/0x107
...

We noticed that commit d3b04a4398 added "select CONFIG_CRYPTO_KDF800108_CTR" in
security/keys/Kconfig, so we speculate that this issue may have connection with
other code controlled by this config, not limited to the code introduced in
this commit. In other words, this is more likely a "For your reference" report.

Regards,
Yujie
View attachment "reproduce.log" of type "text/plain" (50918 bytes)