Re: [PATCH] tpm/eventlog: Use kvmalloc() for event log buffer

["Jarkko Sakkinen" <jarkko@kernel.org>]

On Mon Nov 11, 2024 at 10:43 AM EET, Andy (Linux Ecosystem Engineering) Liang wrote:
> > 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()’s 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#L3
> > > 0
> > > #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?
>
> Please check the attached file. The file has also been uploaded to the SUSE Bugzilla.
> Thank you.

Please create a bug to kernel bugzilla and attach the file on that.

BR, Jarkko