From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 1D05F3B38BF for ; Mon, 27 Jul 2026 16:09:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785168579; cv=none; b=DoGk/5F95eeY1qS0NtqY6IlHQP0qSxnVkrYbSpQ/75EtOcoQfxn7LiEb66tqZweb32CWQ9exjyorkmfJA23HsrXGrQq6S/xtPNfrBJzn/NfCj9Qztv9ijemiruGihLO5e6wPfcNF+HW2yjPyGF4Myc5Ky1ibMHOMtGOV2JpVP+g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785168579; c=relaxed/simple; bh=p46QF4q3YzA0a+QVJNYR0+y4ebsQbmmll0sMz2idgC0=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=uvyOofyRvcy90S2MYKg9VhytSPFu3PvZV5muqBER1nwsnkibCNbnPqMwP4PuyNWxwTSMIktQpkya4GsCgNquwAmdJaDgXX1gP5CmZ/5kDYBw0jnVpk+i76kZg0n6OW4ZcWcykYKrIJiVX/hD1d3JUVIZpbA6FH/Jd6nm/QZDfXQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=FykoNNiW; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FykoNNiW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785168576; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZSfRXRIbpqN7bdv7KoAVPTERQMpHVCEfoQKdU9y9kiE=; b=FykoNNiWIWVVYsKpwJoKngPRfm4646fRRvkqYaMxBymBJd4KvVKJkw1fnSupEhvlO4YLqi 8SyQHOgG8oUJHpeyq/6WDkBcssreIFrUO1qL80yxYtiJPcqDkedb7jy7U1jnV4c7SKPATx KFjUCtw+9tON5psqSt1D0MKM8TwYmy0= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-627-zmip40KzPy-jTsATyJUDfw-1; Mon, 27 Jul 2026 12:09:32 -0400 X-MC-Unique: zmip40KzPy-jTsATyJUDfw-1 X-Mimecast-MFC-AGG-ID: zmip40KzPy-jTsATyJUDfw_1785168571 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7B48B18009C6; Mon, 27 Jul 2026 16:09:30 +0000 (UTC) Received: from [10.44.32.225] (unknown [10.44.32.225]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D34AB30010CC; Mon, 27 Jul 2026 16:09:27 +0000 (UTC) Date: Mon, 27 Jul 2026 18:09:20 +0200 (CEST) From: Mikulas Patocka To: Shukai Ni cc: agk@redhat.com, snitzer@kernel.org, bmarzins@redhat.com, gmazyland@gmail.com, dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org, Jo Van Bulck Subject: Re: [PATCH 1/1] dm-integrity: replace forgeable discard filler with a keyed sector marker In-Reply-To: <20260727134841.1109615-2-shukai.ni@kuleuven.be> Message-ID: <4ab87b60-6d97-9507-8a8a-7a273021e8de@redhat.com> References: <20260727134841.1109615-1-shukai.ni@kuleuven.be> <20260727134841.1109615-2-shukai.ni@kuleuven.be> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Mon, 27 Jul 2026, Shukai Ni wrote: > The discard-block check in dm_integrity_rw_tag() treats a stored tag > of all 0xf6 bytes (DISCARD_FILLER) as proof a block was discarded and > skips HMAC verification. allow_discards is only accepted in > dm-integrity's standalone mode. An attacker with raw write access to > the backing device, but without the integrity key, can stamp any block > with an all-0xf6 tag and have it served as authentic. > > Replace the constant filler with a keyed checksum of (salt || sector) > and no block payload, computed by integrity_discard_checksum(). > > Fixes: 84597a44a9d8 ("dm integrity: add optional discard support") > Co-developed-by: Jo Van Bulck > Signed-off-by: Jo Van Bulck > Signed-off-by: Shukai Ni Hi This breaks backward compatibility for existing volumes. I would add a new option "allow_discards_keyed" that enables this functionality (and store this option also as a flag in the superblock, so that it can't be turned off). Mikulas