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Message-ID: <20161213083948.GA8994@zzz>
Date: Tue, 13 Dec 2016 00:39:48 -0800
From: Eric Biggers <ebiggers3@...il.com>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
LKML <linux-kernel@...r.kernel.org>,
Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
George Spelvin <linux@...izon.com>,
Scott Bauer <sbauer@....utah.edu>, Andi Kleen <ak@...ux.intel.com>,
Andy Lutomirski <luto@...capital.net>,
Greg KH <gregkh@...uxfoundation.org>,
Jean-Philippe Aumasson <jeanphilippe.aumasson@...il.com>,
"Daniel J . Bernstein" <djb@...yp.to>
Subject: Re: [PATCH v3] siphash: add cryptographically secure hashtable
function
On Mon, Dec 12, 2016 at 11:18:32PM +0100, Jason A. Donenfeld wrote:
> + for (; data != end; data += sizeof(u64)) {
> + m = get_unaligned_le64(data);
> + v3 ^= m;
> + SIPROUND;
> + SIPROUND;
> + v0 ^= m;
> + }
> +#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
> + b |= le64_to_cpu(load_unaligned_zeropad(data) & bytemask_from_count(left));
> +#else
Hmm, I don't think you can really do load_unaligned_zeropad() without first
checking for 'left != 0'. The fixup section for load_unaligned_zeropad()
assumes that rounding the pointer down to a word boundary will produce an
address from which an 'unsigned long' can be loaded. But if 'left = 0' and we
happen to be on a page boundary with the next page unmapped, then this will not
be true and the second load will still fault.
Eric
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