> On Thu, 07 Nov 2024 20:31:37 +0100,
> Stefan Berger wrote:
> >
> >
> >
> > On 11/7/24 2:06 PM, Stefan Berger wrote:
> > >
> > >
> > > On 11/7/24 7:38 AM, Takashi Iwai wrote:
> > >> On Thu, 07 Nov 2024 13:17:33 +0100, Paul Menzel wrote:
>> >>>
>> >>> Dear Takashi,
>> >>>
>> >>>
>> >>> Thank you for the patch.
>> >>>
>> >>> Am 07.11.24 um 12:18 schrieb Takashi Iwai:
>> >>>> The TPM2 ACPI table may request a large size for the event log,
>> >>>> and it may be over the max size of kmalloc(). When this happens,
>> >>>> the driver
>> >>>
>> >>> What is kmalloc()ʼs maximum size?
>> >>
>> >> 128kB or so, IIRC.
>> >> And according Andy, the table can be over 4MB.
>> >
>> > Can you copy the contents of the file on that machine and tell us
>> > what size it has:
>> >
>> > cp /sys/kernel/security/tpm0/binary_bios_measurements ./
>>
>> Actually, you may need to have the contents parsed by a user space
>> tool since the driver does not detect where the actual end may be:
>>
>> tsseventextend -if ./binary_bios_measurements -sim -v
>>
>> This may give you a feeling for how much is in that file and then
>> you'd have to truncate it into half for example and see whether it
>> still parses the same. My point is that we haven't seen such
>> excessive-sized logs so far and following the parsing above we may
>> find something like this more useful than allocating possibly large
>> amounts of memory that a buggy ACPI table indicates (+ notify
>> manufacturer):
>>
>> if (len > MAX_TPM_LOG_SIZE) {
>> dev_err(&chip->dev, "Truncated excessive-sized TPM log of %d
>> bytes\n", len);
>> len = MAX_TPM_LOG_SIZE;
>> }
>>
>> If you send me the log I'd look at it.
> It's rather a question Andy; could you check give the requested info?
https://elixir.bootlin.com/linux/v6.8/source/arch/x86/include/asm/page_types.h#L10
#define PAGE_SHIFT 12
#define KMALLOC_SHIFT_MAX (MAX_PAGE_ORDER + PAGE_SHIFT)
https://elixir.bootlin.com/linux/v6.8/source/include/linux/mmzone.h#L30
#define MAX_PAGE_ORDER 10
https://elixir.bootlin.com/linux/v6.8/source/include/linux/slab.h#L309
#define KMALLOC_MAX_SIZE (1UL << KMALLOC_SHIFT_MAX)
The max size = (1UL << MAX_PAGE_ORDER + PAGE_SHIFT) = ( 1UL << (10 + 12)) = 2^22 =4,194,304 (4MB)
For the x86, the max size is 4MB.
> thanks,
> Takashi
