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

[Takashi Iwai <tiwai@suse.de>]

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?


thanks,

Takashi