Re: [RESEND PATCH v2] efi: Only print errors about failing to get certs if EFI vars are found

From: David Hildenbrand <david@redhat.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Javier Martinez Canillas <javierm@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>,
	Hans de Goede <hdegoede@redhat.com>,
	Eric Richter <erichte@linux.ibm.com>,
	James Morris <jmorris@namei.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Mimi Zohar <zohar@linux.ibm.com>,
	Nayna Jain <nayna@linux.ibm.com>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	YueHaibing <yuehaibing@huawei.com>,
	linux-security-module <linux-security-module@vger.kernel.org>
Subject: Re: [RESEND PATCH v2] efi: Only print errors about failing to get certs if EFI vars are found
Date: Fri, 28 Feb 2020 10:58:06 +0100	[thread overview]
Message-ID: <0aa9f445-c4af-96d3-b0d8-8a3ec87c313c@redhat.com> (raw)
In-Reply-To: <CAKv+Gu-OO_YiDWbF2pRBQTGe3FxC5CmjuxCnCwxJmnzRHhEz_g@mail.gmail.com>

On 28.02.20 10:44, Ard Biesheuvel wrote:
> On Fri, 28 Feb 2020 at 10:43, David Hildenbrand <david@redhat.com> wrote:
>>
>> On 28.02.20 10:39, Ard Biesheuvel wrote:
>>> On Fri, 28 Feb 2020 at 10:35, David Hildenbrand <david@redhat.com> wrote:
>>>>
>>>> On 28.02.20 10:31, David Hildenbrand wrote:
>>>>> On 28.02.20 10:19, David Hildenbrand wrote:
>>>>>> On 17.02.20 12:39, Javier Martinez Canillas wrote:
>>>>>>> If CONFIG_LOAD_UEFI_KEYS is enabled, the kernel attempts to load the certs
>>>>>>> from the db, dbx and MokListRT EFI variables into the appropriate keyrings.
>>>>>>>
>>>>>>> But it just assumes that the variables will be present and prints an error
>>>>>>> if the certs can't be loaded, even when is possible that the variables may
>>>>>>> not exist. For example the MokListRT variable will only be present if shim
>>>>>>> is used.
>>>>>>>
>>>>>>> So only print an error message about failing to get the certs list from an
>>>>>>> EFI variable if this is found. Otherwise these printed errors just pollute
>>>>>>> the kernel log ring buffer with confusing messages like the following:
>>>>>>>
>>>>>>> [    5.427251] Couldn't get size: 0x800000000000000e
>>>>>>> [    5.427261] MODSIGN: Couldn't get UEFI db list
>>>>>>> [    5.428012] Couldn't get size: 0x800000000000000e
>>>>>>> [    5.428023] Couldn't get UEFI MokListRT
>>>>>>>
>>>>>>> Reported-by: Hans de Goede <hdegoede@redhat.com>
>>>>>>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>>>>>>> Tested-by: Hans de Goede <hdegoede@redhat.com>
>>>>>>
>>>>>> This patch seems to break a very basic x86-64 QEMU setup (booting
>>>>>> upstream kernel with a F31 initrd - are you running basic boot tests?).
>>>>>> Luckily, it only took me 5 minutes to identify this patch. Reverting
>>>>>> this patch from linux-next fixes it for me.
>>>>>>
>>>>>>
>>>>>> [    1.042766] Loaded X.509 cert 'Build time autogenerated kernel key: 6625d6e34255935276d2c9851e2458909a4bcd69'
>>>>>> [    1.044314] zswap: loaded using pool lzo/zbud
>>>>>> [    1.045663] Key type ._fscrypt registered
>>>>>> [    1.046154] Key type .fscrypt registered
>>>>>> [    1.046524] Key type fscrypt-provisioning registered
>>>>>> [    1.051178] Key type big_key registered
>>>>>> [    1.055108] Key type encrypted registered
>>>>>> [    1.055513] BUG: kernel NULL pointer dereference, address: 0000000000000000
>>>>>> [    1.056172] #PF: supervisor instruction fetch in kernel mode
>>>>>> [    1.056706] #PF: error_code(0x0010) - not-present page
>>>>>> [    1.057367] PGD 0 P4D 0
>>>>>> [    1.057729] Oops: 0010 [#1] SMP NOPTI
>>>>>> [    1.058249] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.6.0-rc3-next-20200228+ #79
>>>>>> [    1.059167] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.4
>>>>>> [    1.060230] RIP: 0010:0x0
>>>>>> [    1.060478] Code: Bad RIP value.
>>>>>> [    1.060786] RSP: 0018:ffffbc7880637d98 EFLAGS: 00010246
>>>>>> [    1.061281] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffbc7880637dc8
>>>>>> [    1.061954] RDX: 0000000000000000 RSI: ffffbc7880637df0 RDI: ffffffffa73c40be
>>>>>> [    1.062611] RBP: ffffbc7880637e20 R08: ffffbc7880637dac R09: ffffa0238f4ba6c0
>>>>>> [    1.063278] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
>>>>>> [    1.063956] R13: ffffa024bdd6f660 R14: 0000000000000000 R15: 0000000000000000
>>>>>> [    1.064609] FS:  0000000000000000(0000) GS:ffffa023fdd00000(0000) knlGS:0000000000000000
>>>>>> [    1.065360] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>> [    1.065900] CR2: ffffffffffffffd6 CR3: 00000000b1610000 CR4: 00000000000006e0
>>>>>> [    1.066562] Call Trace:
>>>>>> [    1.066803]  load_uefi_certs+0xc8/0x2bb
>>>>>> [    1.067171]  ? get_cert_list+0xfb/0xfb
>>>>>> [    1.067523]  do_one_initcall+0x5d/0x2f0
>>>>>> [    1.067894]  ? rcu_read_lock_sched_held+0x52/0x80
>>>>>> [    1.068337]  kernel_init_freeable+0x243/0x2c2
>>>>>> [    1.068751]  ? rest_init+0x23a/0x23a
>>>>>> [    1.069095]  kernel_init+0xa/0x106
>>>>>> [    1.069416]  ret_from_fork+0x27/0x50
>>>>>> [    1.069759] Modules linked in:
>>>>>> [    1.070050] CR2: 0000000000000000
>>>>>> [    1.070361] ---[ end trace fcce9bb4feb21d99 ]---
>>>>>>
>>>>>>
>>>>>
>>>>> Sorry, wrong mail identified, the patch is actually
>>>>>
>>>>> commit 6b75d54d5258ccd655387a00bbe1b00f92f4d965
>>>>> Author: Ard Biesheuvel <ardb@kernel.org>
>>>>> Date:   Sun Feb 16 19:46:25 2020 +0100
>>>>>
>>>>>     integrity: Check properly whether EFI GetVariable() is available
>>>>>
>>>>>     Testing the value of the efi.get_variable function pointer is not
>>>>>
>>>>> which made it work. (not even able to find that patch on lkml ...)
>>>>
>>>> To clarify for Ard, your patch breaks a basic QEMU setup (see above,
>>>> NULL pointer dereference). Reverting your patch from linux-next makes it
>>>> work again.
>>>>
>>>
>>> Does this fix it?
>>>
>>> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
>>> index 41269a95ff85..d1746a579c99 100644
>>> --- a/drivers/firmware/efi/efi.c
>>> +++ b/drivers/firmware/efi/efi.c
>>> @@ -300,12 +300,12 @@ static int __init efisubsys_init(void)
>>>  {
>>>         int error;
>>>
>>> -       if (!efi_enabled(EFI_BOOT))
>>> -               return 0;
>>> -
>>>         if (!efi_enabled(EFI_RUNTIME_SERVICES))
>>>                 efi.runtime_supported_mask = 0;
>>>
>>> +       if (!efi_enabled(EFI_BOOT))
>>> +               return 0;
>>> +
>>>         if (efi.runtime_supported_mask) {
>>>                 /*
>>>                  * Since we process only one efi_runtime_service() at a time, an
>>>
>>
>> Yes, does the trick!
>>
> 
> Thanks, David. I'll get this out and into -next asap.
> 

Thanks for the very fast fix :)

-- 
Thanks,

David / dhildenb