From: Eric Biggers <ebiggers@kernel.org>
To: linux-crypto@vger.kernel.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH] lib/crypto: gf128mul: Hide selection mask values from compilers
Date: Tue, 3 Nov 2026 15:27:26 -0800 [thread overview]
Message-ID: <20261103232726.GJ2281@quark> (raw)
In-Reply-To: <20261031052154.202008-1-ebiggers@kernel.org>
On Fri, Oct 30, 2026 at 10:21:54PM -0700, Eric Biggers wrote:
> Hide selection mask values from compilers, so that they cannot see that
> they are used to select between two values and potentially generate a
> secret-dependent branch. This is not known to be happening here, but we
> might as well be extra careful.
>
> For the cases where the selected values are only 0x87 and 0, change the
> type of the mask to 'unsigned long' so that the compiler is not forced
> to materialize it in a register pair on 32-bit architectures.
>
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> ---
> include/crypto/gf128mul.h | 25 +++++++++----------------
> 1 file changed, 9 insertions(+), 16 deletions(-)
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next
- Eric
prev parent reply other threads:[~2026-11-03 23:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-31 5:21 [PATCH] lib/crypto: gf128mul: Hide selection mask values from compilers Eric Biggers
2026-11-02 9:12 ` Ard Biesheuvel
2026-11-03 23:27 ` Eric Biggers [this message]
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