linux-kernel - Re: [PATCH v2] arch/x86: Fix size overflows in sgx_encl

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Message-ID: <Z8eoW4rUV5U9JUci@kernel.org>
Date: Wed, 5 Mar 2025 03:26:51 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: linux-integrity@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
	Dan Carpenter <dan.carpenter@...aro.org>, linux-sgx@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arch/x86: Fix size overflows in sgx_encl_create()

On Tue, Mar 04, 2025 at 04:30:21PM -0800, Dave Hansen wrote:
> On 3/4/25 16:19, Jarkko Sakkinen wrote:
> > On Tue, Mar 04, 2025 at 04:18:03PM -0800, Dave Hansen wrote:
> >> On 3/4/25 16:06, Jarkko Sakkinen wrote:
> >>> +	/*
> >>> +	 * This is a micro-architectural requirement. ECREATE would detect this
> >>> +	 * too without mentionable overhead but this check guarantees also that
> >>> +	 * the space calculations for EPC and shmem allocations never overflow.
> >>> +	 */
> >>> +	if (!is_power_of_2(secs->size))
> >>> +		return -EINVAL;
> >> Isn't it a plain old documented architectural requirement?
> > Yes, but it requires some explanation why it exists here instead of
> > counting on ECREATE.
> > 
> > What do you suggest?
> 
> 	/*
> 	 * ECREATE would detect this too, but checking here also ensures
> 	 * that the 'encl_size' calculations below can never overflow.
> 	 */

Looks reasonable to me!

BR, Jarkko