On Fri, 08 Nov 2024 09:48:38 +0100,
Liang, Andy (Linux Ecosystem Engineering) wrote:
>
>
> > 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, it was already corrected by Jarkko :)
But what I meant was about the requests:
> cp /sys/kernel/security/tpm0/binary_bios_measurements ./
and
> tsseventextend -if ./binary_bios_measurements -sim -v
mentioned in the above. Could you provide the info?
thanks,
Takashi
