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Message-ID: <0aa9f445-c4af-96d3-b0d8-8a3ec87c313c@redhat.com>
Date: Fri, 28 Feb 2020 10:58:06 +0100
From: David Hildenbrand <david@...hat.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Javier Martinez Canillas <javierm@...hat.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-efi <linux-efi@...r.kernel.org>,
Hans de Goede <hdegoede@...hat.com>,
Eric Richter <erichte@...ux.ibm.com>,
James Morris <jmorris@...ei.org>,
Michael Ellerman <mpe@...erman.id.au>,
Mimi Zohar <zohar@...ux.ibm.com>,
Nayna Jain <nayna@...ux.ibm.com>,
"Serge E. Hallyn" <serge@...lyn.com>,
YueHaibing <yuehaibing@...wei.com>,
linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [RESEND PATCH v2] efi: Only print errors about failing to get
certs if EFI vars are found
On 28.02.20 10:44, Ard Biesheuvel wrote:
> On Fri, 28 Feb 2020 at 10:43, David Hildenbrand <david@...hat.com> wrote:
>>
>> On 28.02.20 10:39, Ard Biesheuvel wrote:
>>> On Fri, 28 Feb 2020 at 10:35, David Hildenbrand <david@...hat.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@...hat.com>
>>>>>>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>>>>>>> Tested-by: Hans de Goede <hdegoede@...hat.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@...nel.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
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