Re: Regression from efi: call get_event_log before ExitBootServices

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 12 March 2018 at 17:01, Jeremy Cline <jeremy@jcline.org> wrote:
> On 03/12/2018 10:56 AM, Ard Biesheuvel wrote:
>> On 12 March 2018 at 14:30, Jeremy Cline <jeremy@jcline.org> wrote:
>>> On 03/12/2018 07:08 AM, Ard Biesheuvel wrote:
>>>> On 10 March 2018 at 10:45, Thiebaud Weksteen <tweek@google.com> wrote:
>>>>> On Fri, Mar 9, 2018 at 5:54 PM Jeremy Cline <jeremy@jcline.org> wrote:
>>>>>
>>>>>> On Fri, Mar 09, 2018 at 10:43:50AM +0000, Thiebaud Weksteen wrote:
>>>>>>> Thanks a lot for trying out the patch!
>>>>>>>
>>>>>>> Please don't modify your install at this stage, I think we are hitting a
>>>>>>> firmware bug and that would be awesome if we can fix how we are
>>>>> handling it.
>>>>>>> So, if we reach that stage in the function it could either be that:
>>>>>>> * The allocation did not succeed, somehow, but the firmware still
>>>>> returned
>>>>>>> EFI_SUCCEED.
>>>>>>> * The size requested is incorrect (I'm thinking something like a 1G of
>>>>>>> log). This would be due to either a miscalculation of log_size
>>>>> (possible)
>>>>>>> or; the returned values of GetEventLog are not correct.
>>>>>>> I'm sending a patch to add checks for these. Could you please apply and
>>>>>>> retest?
>>>>>>> Again, thanks for helping debugging this.
>>>>>
>>>>>> No problem, thanks for the help :)
>>>>>
>>>>>> With the new patch:
>>>>>
>>>>>> Locating the TCG2Protocol
>>>>>> Calling GetEventLog on TCG2Protocol
>>>>>> Log returned
>>>>>> log_location is not empty
>>>>>> log_size != 0
>>>>>> log_size < 1M
>>>>>> Allocating memory for storing the logs
>>>>>> Returned from memory allocation
>>>>>> Copying log to new location
>>>>>
>>>>>> And then it hangs. I added a couple more print statements:
>>>>>
>>>>>> diff --git a/drivers/firmware/efi/libstub/tpm.c
>>>>> b/drivers/firmware/efi/libstub/tpm.c
>>>>>> index ee3fac109078..1ab5638bc50e 100644
>>>>>> --- a/drivers/firmware/efi/libstub/tpm.c
>>>>>> +++ b/drivers/firmware/efi/libstub/tpm.c
>>>>>> @@ -148,8 +148,11 @@ void
>>>>> efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>>>>>>          efi_printk(sys_table_arg, "Copying log to new location\n");
>>>>>
>>>>>>          memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
>>>>>> +       efi_printk(sys_table_arg, "Successfully memset log_tbl to 0\n");
>>>>>>          log_tbl->size = log_size;
>>>>>> +       efi_printk(sys_table_arg, "Set log_tbl->size\n");
>>>>>>          log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
>>>>>> +       efi_printk(sys_table_arg, "Set log_tbl-version\n");
>>>>>>          memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
>>>>>
>>>>>>          efi_printk(sys_table_arg, "Installing the log into the
>>>>> configuration table\n");
>>>>>
>>>>>> and it's hanging at "memset(log_tbl, 0, sizeof(*log_tbl) + log_size);"
>>>>>
>>>>> Thanks. Well, it looks like the memory that is supposedly allocated is not
>>>>> usable. I'm thinking this is a firmware bug.
>>>>> Ard, would you agree on this assumption? Thoughts on how to proceed?
>>>>>
>>>>
>>>> I am rather puzzled why the allocate_pool() should succeed and the
>>>> subsequent memset() should fail. This does not look like an issue that
>>>> is intimately related to TPM2 support, rather an issue in the firmware
>>>> that happens to get tickled after the change.
>>>>
>>>> Would you mind trying replacing EFI_LOADER_DATA with
>>>> EFI_BOOT_SERVICES_DATA in the allocate_pool() call?
>>>
>>> Replacing EFI_LOADER_DATA with EFI_BOOT_SERVICES_DATA still hangs at the
>>> memset() call.
>>>
>>
>> Could you try the following please? (attached as well in case gmail mangles it)
>>
>> diff --git a/drivers/firmware/efi/libstub/tpm.c
>> b/drivers/firmware/efi/libstub/tpm.c
>> index 2298560cea72..30d960a344b7 100644
>> --- a/drivers/firmware/efi/libstub/tpm.c
>> +++ b/drivers/firmware/efi/libstub/tpm.c
>> @@ -70,6 +70,8 @@ void
>> efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>>         size_t log_size, last_entry_size;
>>         efi_bool_t truncated;
>>         void *tcg2_protocol;
>> +       unsigned long num_pages;
>> +       efi_physical_addr_t log_tbl_alloc;
>>
>>         status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
>>                                 &tcg2_protocol);
>> @@ -104,9 +106,12 @@ void
>> efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>>         }
>>
>>         /* Allocate space for the logs and copy them. */
>> -       status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
>> -                               sizeof(*log_tbl) + log_size,
>> -                               (void **) &log_tbl);
>> +       num_pages = DIV_ROUND_UP(sizeof(*log_tbl) + log_size, EFI_PAGE_SIZE);
>> +       status = efi_call_early(allocate_pages,
>> +                               EFI_ALLOCATE_ANY_PAGES,
>> +                               EFI_LOADER_DATA,
>> +                               num_pages,
>> +                               &log_tbl_alloc);
>>
>>         if (status != EFI_SUCCESS) {
>>                 efi_printk(sys_table_arg,
>> @@ -114,6 +119,7 @@ void
>> efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>>                 return;
>>         }
>>
>> +       log_tbl = (struct linux_efi_tpm_eventlog *)(unsigned long)log_tbl_alloc;
>>         memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
>>         log_tbl->size = log_size;
>>         log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
>> @@ -126,7 +132,7 @@ void
>> efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>>         return;
>>
>>  err_free:
>> -       efi_call_early(free_pool, log_tbl);
>> +       efi_call_early(free_pages, log_tbl_alloc, num_pages);
>>  }
>>
>>  void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg)
>>
>
> Hi Ard,
>
> When I apply this, it starts hanging at
>
> status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol,
>                         EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2,
>                         &log_location, &log_last_entry, &truncated);
>
> rather than at the memset() call.
>

That is *very* surprising, given that the change only affects code
that executes after that.

I understand how annoying this is for you, and I think we should try
to fix this, but reverting the patches outright isn't the solution
either.

Which UEFI vendor and version does your system report?