linux-kernel - Re: [PATCH] tpm: Map the ACPI provided event log

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Message-Id: <D6IC7BH3A75U.31VJX6T6QRKKI@kernel.org>
Date: Sun, 22 Dec 2024 17:33:26 +0200
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Jarkko Sakkinen" <jarkko.sakkinen@....fi>, "James Bottomley"
 <James.Bottomley@...senPartnership.com>, "Ard Biesheuvel" <ardb@...nel.org>
Cc: <linux-integrity@...r.kernel.org>, "Peter Huewe" <peterhuewe@....de>,
 "Jason Gunthorpe" <jgg@...pe.ca>, "Colin Ian King"
 <colin.i.king@...il.com>, "Joe Hattori" <joe@...is.s.u-tokyo.ac.jp>,
 "Stefan Berger" <stefanb@...ux.ibm.com>, "Roberto Sassu"
 <roberto.sassu@...wei.com>, "Al Viro" <viro@...iv.linux.org.uk>, "Andy
 Liang" <andy.liang@....com>, "Matthew Garrett" <mjg59@...f.ucam.org>, "Mimi
 Zohar" <zohar@...ux.ibm.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: Map the ACPI provided event log

On Sun Dec 22, 2024 at 5:23 PM EET, Jarkko Sakkinen wrote:
> On Sun Dec 22, 2024 at 5:00 PM EET, James Bottomley wrote:
> > If event logs grow to greater than KMALLOC_MAX_SIZE then absolutely it
> > makes sense to map them instead of copying them.  But we'd have to do
> > that for all event log locators: ACPI, EFI and OF, because event log
> > size should be independent of the mechanism used to locate it.  So,
> > even as a long term fix (assuming we think there's a possibility of
> > logs expanding by 50x), this patch doesn't do the right thing because
> > it only maps ACPI logs.
>
> Because we have a test target only on ACPI where this happens fix
> should still fix only ACPI. It's not hard to reiterate this but 
> precursory iteration is a bad idea.

Also, "event log size should be independent of the mechanism used to
locate it" is a sentence that is sky high too abstract to say much.

I don't know what it means to be frank.

BR, Jarkko