From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 19 Jun 2020 13:46:14 -0400 From: Vivek Goyal Message-ID: <20200619174614.GG3154@redhat.com> References: <20200619171809.30984-1-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200619171809.30984-1-dgilbert@redhat.com> Subject: Re: [Virtio-fs] [PATCH] virtiofsd: Allow capability restriction to be turned off List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org On Fri, Jun 19, 2020 at 06:18:09PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > Commit a59feb483b8fae24d043 dropped most capabilities at startup, > since in most cases virtiofsd doesn't need them. Unfortunately we found > a case that needs CAP_SYS_ADMIN - setting trusted extended attributes. > It's rare to need it, and the clean fix for it is going to be more > complicated, but as a way for existing users to continue, allow the > capability restriction to be turned off by adding > > -o no_restrictcaps > > We still drop the capabilities by default since this seems much safer; > even if we don't have an explicit problem to fix. > Hi David, In one of the emails, Daniel suggested option "--trusted-xattrs=on|off". How about we use that and if that option is specified, we automatically give CAP_SYS_ADMIN as well. Something to consider. This probably could be extended later to "--trusted-xattrs=on|off|remapped" when we have the capability to remap. And in case of "off/remap" we can take away CAP_SYS_ADMIN. Vivek > Signed-off-by: Dr. David Alan Gilbert > --- > docs/tools/virtiofsd.rst | 3 +++ > tools/virtiofsd/helper.c | 3 +++ > tools/virtiofsd/passthrough_ll.c | 8 +++++++- > 3 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst > index 378594c422..8819d7d19e 100644 > --- a/docs/tools/virtiofsd.rst > +++ b/docs/tools/virtiofsd.rst > @@ -81,6 +81,9 @@ Options > Enable/disable extended attributes (xattr) on files and directories. The > default is ``no_xattr``. > > + * restrictcaps|no_restrictcaps\n" > + Restrict capabilities at startup. The default is ``restrictcaps``. > + > .. option:: --socket-path=PATH > > Listen on vhost-user UNIX domain socket at PATH. > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > index 00a1ef666a..51ed9fbed0 100644 > --- a/tools/virtiofsd/helper.c > +++ b/tools/virtiofsd/helper.c > @@ -174,6 +174,9 @@ void fuse_cmdline_help(void) > " default: no_writeback\n" > " -o xattr|no_xattr enable/disable xattr\n" > " default: no_xattr\n" > + " -o restrictcaps|no_restrictcaps\n" > + " restrict capabilities at startup\n" > + " default: restrictcaps\n" > " --rlimit-nofile= set maximum number of file descriptors\n" > " (0 leaves rlimit unchanged)\n" > " default: min(1000000, fs.file-max - 16384)\n" > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 2ce7c96085..8dee657b19 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -144,6 +144,7 @@ struct lo_data { > int flock; > int posix_lock; > int xattr; > + int restrictcaps; > char *source; > double timeout; > int cache; > @@ -170,6 +171,8 @@ static const struct fuse_opt lo_opts[] = { > { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 }, > { "xattr", offsetof(struct lo_data, xattr), 1 }, > { "no_xattr", offsetof(struct lo_data, xattr), 0 }, > + { "restrictcaps", offsetof(struct lo_data, restrictcaps), 1 }, > + { "no_restrictcaps", offsetof(struct lo_data, restrictcaps), 0 }, > { "timeout=%lf", offsetof(struct lo_data, timeout), 0 }, > { "timeout=", offsetof(struct lo_data, timeout_set), 1 }, > { "cache=none", offsetof(struct lo_data, cache), CACHE_NONE }, > @@ -2615,7 +2618,9 @@ static void setup_sandbox(struct lo_data *lo, struct fuse_session *se, > setup_namespaces(lo, se); > setup_mounts(lo->source); > setup_seccomp(enable_syslog); > - setup_capabilities(); > + if (lo->restrictcaps) { > + setup_capabilities(); > + } > } > > /* Set the maximum number of open file descriptors */ > @@ -2764,6 +2769,7 @@ int main(int argc, char *argv[]) > .writeback = 0, > .posix_lock = 1, > .proc_self_fd = -1, > + .restrictcaps = 1, > }; > struct lo_map_elem *root_elem; > int ret = -1; > -- > 2.26.2 > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BEAEC433DF for ; Fri, 19 Jun 2020 17:47:16 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F14312100A for ; Fri, 19 Jun 2020 17:47:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bFyFwY1M" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F14312100A Authentication-Results: mail.kernel.org; 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Fri, 19 Jun 2020 17:46:14 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 2C961220390; Fri, 19 Jun 2020 13:46:14 -0400 (EDT) Date: Fri, 19 Jun 2020 13:46:14 -0400 From: Vivek Goyal To: "Dr. David Alan Gilbert (git)" Subject: Re: [PATCH] virtiofsd: Allow capability restriction to be turned off Message-ID: <20200619174614.GG3154@redhat.com> References: <20200619171809.30984-1-dgilbert@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200619171809.30984-1-dgilbert@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=vgoyal@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/19 03:15:03 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_H3=-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, stefanha@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Jun 19, 2020 at 06:18:09PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > Commit a59feb483b8fae24d043 dropped most capabilities at startup, > since in most cases virtiofsd doesn't need them. Unfortunately we found > a case that needs CAP_SYS_ADMIN - setting trusted extended attributes. > It's rare to need it, and the clean fix for it is going to be more > complicated, but as a way for existing users to continue, allow the > capability restriction to be turned off by adding > > -o no_restrictcaps > > We still drop the capabilities by default since this seems much safer; > even if we don't have an explicit problem to fix. > Hi David, In one of the emails, Daniel suggested option "--trusted-xattrs=on|off". How about we use that and if that option is specified, we automatically give CAP_SYS_ADMIN as well. Something to consider. This probably could be extended later to "--trusted-xattrs=on|off|remapped" when we have the capability to remap. And in case of "off/remap" we can take away CAP_SYS_ADMIN. Vivek > Signed-off-by: Dr. David Alan Gilbert > --- > docs/tools/virtiofsd.rst | 3 +++ > tools/virtiofsd/helper.c | 3 +++ > tools/virtiofsd/passthrough_ll.c | 8 +++++++- > 3 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst > index 378594c422..8819d7d19e 100644 > --- a/docs/tools/virtiofsd.rst > +++ b/docs/tools/virtiofsd.rst > @@ -81,6 +81,9 @@ Options > Enable/disable extended attributes (xattr) on files and directories. The > default is ``no_xattr``. > > + * restrictcaps|no_restrictcaps\n" > + Restrict capabilities at startup. The default is ``restrictcaps``. > + > .. option:: --socket-path=PATH > > Listen on vhost-user UNIX domain socket at PATH. > diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > index 00a1ef666a..51ed9fbed0 100644 > --- a/tools/virtiofsd/helper.c > +++ b/tools/virtiofsd/helper.c > @@ -174,6 +174,9 @@ void fuse_cmdline_help(void) > " default: no_writeback\n" > " -o xattr|no_xattr enable/disable xattr\n" > " default: no_xattr\n" > + " -o restrictcaps|no_restrictcaps\n" > + " restrict capabilities at startup\n" > + " default: restrictcaps\n" > " --rlimit-nofile= set maximum number of file descriptors\n" > " (0 leaves rlimit unchanged)\n" > " default: min(1000000, fs.file-max - 16384)\n" > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 2ce7c96085..8dee657b19 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -144,6 +144,7 @@ struct lo_data { > int flock; > int posix_lock; > int xattr; > + int restrictcaps; > char *source; > double timeout; > int cache; > @@ -170,6 +171,8 @@ static const struct fuse_opt lo_opts[] = { > { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 }, > { "xattr", offsetof(struct lo_data, xattr), 1 }, > { "no_xattr", offsetof(struct lo_data, xattr), 0 }, > + { "restrictcaps", offsetof(struct lo_data, restrictcaps), 1 }, > + { "no_restrictcaps", offsetof(struct lo_data, restrictcaps), 0 }, > { "timeout=%lf", offsetof(struct lo_data, timeout), 0 }, > { "timeout=", offsetof(struct lo_data, timeout_set), 1 }, > { "cache=none", offsetof(struct lo_data, cache), CACHE_NONE }, > @@ -2615,7 +2618,9 @@ static void setup_sandbox(struct lo_data *lo, struct fuse_session *se, > setup_namespaces(lo, se); > setup_mounts(lo->source); > setup_seccomp(enable_syslog); > - setup_capabilities(); > + if (lo->restrictcaps) { > + setup_capabilities(); > + } > } > > /* Set the maximum number of open file descriptors */ > @@ -2764,6 +2769,7 @@ int main(int argc, char *argv[]) > .writeback = 0, > .posix_lock = 1, > .proc_self_fd = -1, > + .restrictcaps = 1, > }; > struct lo_map_elem *root_elem; > int ret = -1; > -- > 2.26.2 >