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

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Message-ID: <Z8eUcELiMdcM5IJq@kernel.org>
Date: Wed, 5 Mar 2025 02:01:52 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: linux-sgx@...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-kernel@...r.kernel.org
Subject: Re: [PATCH] arch/x86: Fix size overflows in sgx_encl_create()

On Tue, Mar 04, 2025 at 03:30:54PM -0800, Dave Hansen wrote:
> On 3/4/25 14:56, Jarkko Sakkinen wrote:
> > The total size calculated for EPC can overflow u64 given the added up page
> > for SECS.  Further, the total size calculated for shmem can overflow even
> > when the EPC size stays within limits of u64, given that it adds the extra
> > space for 128 byte PCMD structures (one for each page).
> > 
> > Address this by adding the necessary validation for each partial results
> > before going forward. Return -E2BIG when an overflow is detected.
> 
> Wouldn't this be a lot simpler if we just had some sane limit that's
> *FAR* below where u64 will overflow?

Yes, we can simply check right at the get go that the uarch requirement
of SGX is satisfied: secs->size is power of two.

BR, Jarkko