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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:60262 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jm03F-00069P-Iw for qemu-devel@archiver.kernel.org; Thu, 18 Jun 2020 15:18:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39026) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jm02B-0004Tn-D4 for qemu-devel@nongnu.org; Thu, 18 Jun 2020 15:17:11 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:28245) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jm029-0000hh-70 for qemu-devel@nongnu.org; Thu, 18 Jun 2020 15:17:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592507827; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3+2fuwaYdUbo9Lf+Fd2YZ6DhXG5dCOvxVeE6Ups1ArI=; b=ZdtwPM5o1esqEHglKKhuwfyDS3KfxdRyST415psI5E45FKecKIfGxgOf3hSnjf1NNLVAv4 7cgdQ+W/25Y6WsrfrUgsPbMVngESbBW2X6C2B1oomlgof17nyvKDNKRRiGAcnDL3LmkfaK pViBzFjAxXIh0lR12NqylJiwHP0e3/E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-21-OIcOXzDxPXu1bW6pIdw5eA-1; Thu, 18 Jun 2020 15:17:05 -0400 X-MC-Unique: OIcOXzDxPXu1bW6pIdw5eA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8BB1010059A1; Thu, 18 Jun 2020 19:17:04 +0000 (UTC) Received: from work-vm (ovpn-114-205.ams2.redhat.com [10.36.114.205]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 02E855C1D0; Thu, 18 Jun 2020 19:16:57 +0000 (UTC) Date: Thu, 18 Jun 2020 20:16:55 +0100 From: "Dr. David Alan Gilbert" To: Vivek Goyal Subject: Re: [Virtio-fs] [PATCH 0/2] virtiofsd: drop Linux capabilities(7) Message-ID: <20200618191655.GI2769@work-vm> References: <20200416164907.244868-1-stefanha@redhat.com> <20200618190816.GD3814@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200618190816.GD3814@redhat.com> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/18 00:57:40 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org, Stefan Hajnoczi , Miklos Szeredi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Vivek Goyal (vgoyal@redhat.com) wrote: > On Thu, Apr 16, 2020 at 05:49:05PM +0100, Stefan Hajnoczi wrote: > > virtiofsd doesn't need of all Linux capabilities(7) available to root. Keep a > > whitelisted set of capabilities that we require. This improves security in > > case virtiofsd is compromised by making it hard for an attacker to gain further > > access to the system. > > Hi Stefan, > > I just noticed that this patch set breaks overlayfs on top of virtiofs. > > overlayfs sets "trusted.overlay.*" and xattrs in trusted domain > need CAP_SYS_ADMIN. > > man xattr says. > > Trusted extended attributes > Trusted extended attributes are visible and accessible only to pro‐ > cesses that have the CAP_SYS_ADMIN capability. Attributes in this > class are used to implement mechanisms in user space (i.e., outside the > kernel) which keep information in extended attributes to which ordinary > processes should not have access. > > There is a chance that overlay moves away from trusted xattr in future. > But for now we need to make it work. This is an important use case for > kata docker in docker build. > > May be we can add an option to virtiofsd say "--add-cap " and > ask user to pass in "--add-cap cap_sys_admin" if they need to run daemon > with this capaibility. I'll admit I don't like the idea of giving it cap_sys_admin. Can you explain: a) What overlayfs uses trusted for? b) If something nasty was to write junk into the trusted attributes, what would happen? c) I see overlayfs has a fallback check if xattr isn't supported at all - what is the consequence? Dave > Thanks > Vivek > > > > > Stefan Hajnoczi (2): > > virtiofsd: only retain file system capabilities > > virtiofsd: drop all capabilities in the wait parent process > > > > tools/virtiofsd/passthrough_ll.c | 51 ++++++++++++++++++++++++++++++++ > > 1 file changed, 51 insertions(+) > > > > -- > > 2.25.1 > > > > _______________________________________________ > > Virtio-fs mailing list > > Virtio-fs@redhat.com > > https://www.redhat.com/mailman/listinfo/virtio-fs > > _______________________________________________ > Virtio-fs mailing list > Virtio-fs@redhat.com > https://www.redhat.com/mailman/listinfo/virtio-fs -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK