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Date: Fri, 9 Feb 2024 21:09:12 -0800
From: Andi Kleen <ak@linux.intel.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: x86@kernel.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
	Daniel P =?iso-8859-1?Q?=2E_Berrang=E9?= <berrange@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Elena Reshetova <elena.reshetova@intel.com>,
	"H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Theodore Ts'o <tytso@mit.edu>, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86/coco: Require seeding RNG with RDRAND on CoCo systems
Message-ID: <ZccE-LzC3uKyxdGa@tassilo>
References: <20240209164946.4164052-1-Jason@zx2c4.com>
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> +	for (i = 0; i < ARRAY_SIZE(rng_seed); i += longs) {
> +		longs = arch_get_random_longs(&rng_seed[i], ARRAY_SIZE(rng_seed) - i);
> +
> +		/*
> +		 * A zero return value means that the guest is under attack,
> +		 * the hardware is broken, or some other mishap has occurred
> +		 * that means the RNG cannot be properly rng_seeded, which also
> +		 * likely means most crypto inside of the CoCo instance will be
> +		 * broken, defeating the purpose of CoCo in the first place. So
> +		 * just panic here because it's absolutely unsafe to continue
> +		 * executing.
> +		 */
> +		BUG_ON(longs == 0);

BUG_ON doesn't necessarily panic. If you want panic, use panic.

-Andi