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bh=xZfq79Da3uTkittJEqhUW+Oi6C5CdJ7LzHr0GuC9EyY=; b=IVKUFv0iBn2sEay3rdTrteH4hxViLiLucU3XTywUC3xICS/ocxPEejjbthWftkDdsXm7EO xchKKThQq+5zXfC3JvgqrwHTtgdy/MVMP9uLA4n1xySd38NdqQWOQGNF3NP6VJkM4TJUly aTSLLfA6nI44CrjqeQNzS8YWshLd+lM= 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-578-f1VbjurHPKSsg0eF3Cf7jg-1; Mon, 15 Feb 2021 10:57:23 -0500 X-MC-Unique: f1VbjurHPKSsg0eF3Cf7jg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2A7F2106BB24 for ; Mon, 15 Feb 2021 15:57:22 +0000 (UTC) Received: from localhost (ovpn-113-245.ams2.redhat.com [10.36.113.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9BC845D9C0; Mon, 15 Feb 2021 15:57:12 +0000 (UTC) Date: Mon, 15 Feb 2021 15:57:11 +0000 From: Stefan Hajnoczi To: Vivek Goyal Subject: Re: [PATCH 23/24] vhost-user-fs: Implement drop CAP_FSETID functionality Message-ID: <20210215155711.GA95852@stefanha-x1.localdomain> References: <20210209190224.62827-1-dgilbert@redhat.com> <20210209190224.62827-24-dgilbert@redhat.com> <20210211143542.GT247031@stefanha-x1.localdomain> <20210211144031.GB5014@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210211144031.GB5014@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="d6Gm4EdcadzBjdND" Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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, marcandre.lureau@redhat.com, mst@redhat.com, "Dr. David Alan Gilbert \(git\)" , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --d6Gm4EdcadzBjdND Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Feb 11, 2021 at 09:40:31AM -0500, Vivek Goyal wrote: > On Thu, Feb 11, 2021 at 02:35:42PM +0000, Stefan Hajnoczi wrote: > > On Tue, Feb 09, 2021 at 07:02:23PM +0000, Dr. David Alan Gilbert (git) = wrote: > > > From: Vivek Goyal > > >=20 > > > As part of slave_io message, slave can ask to do I/O on an fd. Additi= onally > > > slave can ask for dropping CAP_FSETID (if master has it) before doing= I/O. > > > Implement functionality to drop CAP_FSETID and gain it back after the > > > operation. > > >=20 > > > This also creates a dependency on libcap-ng. > >=20 > > Is this patch only for the case where QEMU is running as root? > >=20 >=20 > Yes, it primarily is for the case where qemu is running as root, or > somebody managed to launch it non-root but with still having capability > CAP_FSETID. Running QEMU as root is not encouraged because the security model is designed around the principle of least privilege (only give QEMU access to resources that belong to the guest). What happens in the case where QEMU is not root? Does that mean QEMU will drop suid/guid bits even if the FUSE client wanted them to be preserved? 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