From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2C0481A0728; Sat, 18 Jul 2026 18:38:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784399883; cv=none; b=snlK3m52KITrm2j+fh/fpw64giG+tiChQVI4ibgxRBEbYrO5VYMWU2BbIXy9EPU/A4tMTRjCNECtdJoAY1VPMs+uTLuH09Ifgbsh7KHEqDyZG+H2SQurkGkF5ygXuxwSFzWYVO/AXlZXYaG8b0zjvHNGXldLi1Irp/tPDO/Lkh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784399883; c=relaxed/simple; bh=yTpfi5evPdzYgpJNBWuSyVaW924Va8IbbwvNtn6v4zY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=M6aKqS1ngwA6ovbYv0JCk2MUJPOQ8aacbqr5+2g5CvcDDijgfsO0URjM5fhmHa5F+/+Wmx/ih4mmJZvy3GjS2smCgsvLcdG74j862Q1TCDENrinUkOWBdNUMEnlnoOA6of9HUefpThXU9JOXkyvkr+jXCTEl31GP3JJkSx5L8L0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EvEKeHWh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EvEKeHWh" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id F26A01F000E9; Sat, 18 Jul 2026 18:38:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784399881; bh=E3zzHuHP0j4uCuo0L4YoYxnqoGQ+xsWpY7i4//7Q6jc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=EvEKeHWhKIraQ9Lm6R+gajjEqjGZDPBSM8UTbQtcrBRSsa5UJaF3+yk4oKfdZqMv3 Lw5FuO1p2rqbYWKXgU41f4OncMwI2PgB4XQyXq1bRjx6Pq7FbS/ywKp5WawHHU67b5 SBQtcFz69HUfBg2jYr1wklWjdLrI6vZIwKG7b7fgG5PFdXIwo7eoRD/d3YjvUC3XDC TLfOYIi4lQLYAFg83Rq6cIbqqg0wfEWpUeHE7Pl47cMO1ADrWtkOa6ai14T/TVc86X RcrlH7lazIj9OgwgJWAWbyuXu5mP+vWeOf3ljc+SjFL1OW0OCcyja2qXl2bdcNcbaZ q80foPyU+PW2g== Date: Sat, 18 Jul 2026 21:37:58 +0300 From: Jarkko Sakkinen To: Michael Bommarito Cc: David Howells , Andrew Morton , Paul Moore , James Morris , "Serge E . Hallyn" , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] assoc_array: trim the final shortcut word using the current chunk end Message-ID: References: <20260714115451.3773164-1-michael.bommarito@gmail.com> <20260714115451.3773164-4-michael.bommarito@gmail.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260714115451.3773164-4-michael.bommarito@gmail.com> On Tue, Jul 14, 2026 at 07:54:51AM -0400, Michael Bommarito wrote: > assoc_array_walk() masks off the bits past shortcut->skip_to_level in the > word that contains skip_to_level, gated on > round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > skip_to_level. > > That guard is wrong in two opposite ways: > > - When sc_level is word-aligned (every word after the first) round_up() > is a no-op, so the guard is sc_level > skip_to_level and never fires for > the word that holds skip_to_level. A shortcut that spans more than one > word and ends in the middle of its last word leaves that word untrimmed, > and its stale high bits leak into the dissimilarity word and can steer > the walk down the wrong descendant. > > - When sc_level is unaligned (the first word) and skip_to_level sits on > the next chunk boundary, sc_level + CHUNK would exceed skip_to_level and > fire the trim with shift = skip_to_level & CHUNK_MASK == 0, which clears > the whole dissimilarity word and makes a differing shortcut compare > equal. > > Use the end of the chunk that contains sc_level instead: > > skip_to_level < round_down(sc_level, CHUNK) + CHUNK > > For an aligned sc_level whose word holds skip_to_level this now fires (the > first bug); for an unaligned sc_level with skip_to_level on the following > boundary it does not, so shift is never 0 when the branch runs and the trim > never clears the whole word. > > Fixes: 3cb989501c26 ("Add a generic associative array implementation.") > Assisted-by: Claude:claude-opus-4-8 > Signed-off-by: Michael Bommarito > --- > lib/assoc_array.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/lib/assoc_array.c b/lib/assoc_array.c > index bcc6e0a013eb8..b6c9723e12ced 100644 > --- a/lib/assoc_array.c > +++ b/lib/assoc_array.c > @@ -255,7 +255,8 @@ assoc_array_walk(const struct assoc_array *array, > sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT]; > dissimilarity = segments ^ sc_segments; > > - if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) { > + if (shortcut->skip_to_level < round_down(sc_level, > + ASSOC_ARRAY_KEY_CHUNK_SIZE) + ASSOC_ARRAY_KEY_CHUNK_SIZE) { > /* Trim segments that are beyond the shortcut */ > int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK; > dissimilarity &= ~(ULONG_MAX << shift); > -- > 2.53.0 > Reviewed-by: Jarkko Sakkinen BR, Jarkko