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

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Message-ID: <379e2198-55bb-4fd9-bf54-7fe0b3e33803@intel.com>
Date: Tue, 4 Mar 2025 16:30:21 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
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 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.
	 */