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[82.29.237.198]) by smtp.gmail.com with ESMTPSA id t128sm267343wma.41.2021.06.28.11.26.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Jun 2021 11:26:22 -0700 (PDT) Date: Mon, 28 Jun 2021 19:26:20 +0100 From: "Dr. David Alan Gilbert" To: Vivek Goyal Subject: Re: [PATCH v7 7/7] virtiofsd: Add an option to enable/disable posix acls Message-ID: References: <20210622150852.1507204-1-vgoyal@redhat.com> <20210622150852.1507204-8-vgoyal@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210622150852.1507204-8-vgoyal@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) 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=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.375, 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, miklos@szeredi.hu, qemu-devel@nongnu.org, lhenriques@suse.de Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Vivek Goyal (vgoyal@redhat.com) wrote: > fuse has an option FUSE_POSIX_ACL which needs to be opted in by fuse > server to enable posix acls. As of now we are not opting in for this, > so posix acls are disabled on virtiofs by default. > > Add virtiofsd option "-o posix_acl/no_posix_acl" to let users enable/disable > posix acl support. By default it is disabled as of now due to performance > concerns with cache=none. > > Currently even if file server has not opted in for FUSE_POSIX_ACL, user can > still query acl and set acl, and system.posix_acl_access and > system.posix_acl_default xattrs show up listxattr response. > > Miklos said this is confusing. So he said lets block and filter > system.posix_acl_access and system.posix_acl_default xattrs in > getxattr/setxattr/listxattr if user has explicitly disabled > posix acls using -o no_posix_acl. > > As of now continuing to keeping the existing behavior if user did not > specify any option to disable acl support due to concerns about backward > compatibility. > > Signed-off-by: Vivek Goyal Reviewed-by: Dr. David Alan Gilbert (I'd have some sympathy to making get silently hide it) > --- > docs/tools/virtiofsd.rst | 3 + > tools/virtiofsd/helper.c | 1 + > tools/virtiofsd/passthrough_ll.c | 115 ++++++++++++++++++++++++++++++- > 3 files changed, 118 insertions(+), 1 deletion(-) > > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst > index 00554c75bd..a41f934999 100644 > --- a/docs/tools/virtiofsd.rst > +++ b/docs/tools/virtiofsd.rst > @@ -101,6 +101,9 @@ Options > Enable/disable extended attributes (xattr) on files and directories. The > default is ``no_xattr``. > > + * posix_acl|no_posix_acl - > + Enable/disable posix acl support. Posix ACLs are disabled by default`. > + > .. 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 5e98ed702b..a8295d975a 100644 > --- a/tools/virtiofsd/helper.c > +++ b/tools/virtiofsd/helper.c > @@ -186,6 +186,7 @@ void fuse_cmdline_help(void) > " to virtiofsd from guest applications.\n" > " default: no_allow_direct_io\n" > " -o announce_submounts Announce sub-mount points to the guest\n" > + " -o posix_acl/no_posix_acl Enable/Disable posix_acl. (default: disabled)\n" > ); > } > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 113c725def..e80fd76d71 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -175,7 +175,7 @@ struct lo_data { > int user_killpriv_v2, killpriv_v2; > /* If set, virtiofsd is responsible for setting umask during creation */ > bool change_umask; > - int posix_acl; > + int user_posix_acl, posix_acl; > }; > > static const struct fuse_opt lo_opts[] = { > @@ -208,6 +208,8 @@ static const struct fuse_opt lo_opts[] = { > { "announce_submounts", offsetof(struct lo_data, announce_submounts), 1 }, > { "killpriv_v2", offsetof(struct lo_data, user_killpriv_v2), 1 }, > { "no_killpriv_v2", offsetof(struct lo_data, user_killpriv_v2), 0 }, > + { "posix_acl", offsetof(struct lo_data, user_posix_acl), 1 }, > + { "no_posix_acl", offsetof(struct lo_data, user_posix_acl), 0 }, > FUSE_OPT_END > }; > static bool use_syslog = false; > @@ -706,6 +708,32 @@ static void lo_init(void *userdata, struct fuse_conn_info *conn) > conn->want &= ~FUSE_CAP_HANDLE_KILLPRIV_V2; > lo->killpriv_v2 = 0; > } > + > + if (lo->user_posix_acl == 1) { > + /* > + * User explicitly asked for this option. Enable it unconditionally. > + * If connection does not have this capability, print error message > + * now. It will fail later in fuse_lowlevel.c > + */ > + if (!(conn->capable & FUSE_CAP_POSIX_ACL) || > + !(conn->capable & FUSE_CAP_DONT_MASK) || > + !(conn->capable & FUSE_CAP_SETXATTR_EXT)) { > + fuse_log(FUSE_LOG_ERR, "lo_init: Can not enable posix acl." > + " kernel does not support FUSE_POSIX_ACL, FUSE_DONT_MASK" > + " or FUSE_SETXATTR_EXT capability.\n"); > + } else { > + fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling posix acl\n"); > + } > + > + conn->want |= FUSE_CAP_POSIX_ACL | FUSE_CAP_DONT_MASK | > + FUSE_CAP_SETXATTR_EXT; > + lo->change_umask = true; > + lo->posix_acl = true; > + } else { > + /* User either did not specify anything or wants it disabled */ > + fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling posix_acl\n"); > + conn->want &= ~FUSE_CAP_POSIX_ACL; > + } > } > > static void lo_getattr(fuse_req_t req, fuse_ino_t ino, > @@ -2783,6 +2811,63 @@ static int xattr_map_server(const struct lo_data *lo, const char *server_name, > assert(fchdir_res == 0); \ > } while (0) > > +static bool block_xattr(struct lo_data *lo, const char *name) > +{ > + /* > + * If user explicitly enabled posix_acl or did not provide any option, > + * do not block acl. Otherwise block system.posix_acl_access and > + * system.posix_acl_default xattrs. > + */ > + if (lo->user_posix_acl) { > + return false; > + } > + if (!strcmp(name, "system.posix_acl_access") || > + !strcmp(name, "system.posix_acl_default")) > + return true; > + > + return false; > +} > + > +/* > + * Returns number of bytes in xattr_list after filtering on success. This > + * could be zero as well if nothing is left after filtering. > + * > + * Returns negative error code on failure. > + * xattr_list is modified in place. > + */ > +static int remove_blocked_xattrs(struct lo_data *lo, char *xattr_list, > + unsigned in_size) > +{ > + size_t out_index, in_index; > + > + /* > + * As of now we only filter out acl xattrs. If acls are enabled or > + * they have not been explicitly disabled, there is nothing to > + * filter. > + */ > + if (lo->user_posix_acl) { > + return in_size; > + } > + > + out_index = 0; > + in_index = 0; > + while (in_index < in_size) { > + char *in_ptr = xattr_list + in_index; > + > + /* Length of current attribute name */ > + size_t in_len = strlen(xattr_list + in_index) + 1; > + > + if (!block_xattr(lo, in_ptr)) { > + if (in_index != out_index) { > + memmove(xattr_list + out_index, xattr_list + in_index, in_len); > + } > + out_index += in_len; > + } > + in_index += in_len; > + } > + return out_index; > +} > + > static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, > size_t size) > { > @@ -2796,6 +2881,11 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, > int saverr; > int fd = -1; > > + if (block_xattr(lo, in_name)) { > + fuse_reply_err(req, EOPNOTSUPP); > + return; > + } > + > mapped_name = NULL; > name = in_name; > if (lo->xattrmap) { > @@ -2986,6 +3076,12 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) > goto out; > } > } > + > + ret = remove_blocked_xattrs(lo, value, ret); > + if (ret <= 0) { > + saverr = -ret; > + goto out; > + } > fuse_reply_buf(req, value, ret); > } else { > /* > @@ -3026,6 +3122,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, > bool cap_fsetid_dropped = false; > struct lo_cred old = {}; > > + if (block_xattr(lo, in_name)) { > + fuse_reply_err(req, EOPNOTSUPP); > + return; > + } > + > mapped_name = NULL; > name = in_name; > if (lo->xattrmap) { > @@ -3118,6 +3219,11 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *in_name) > int saverr; > int fd = -1; > > + if (block_xattr(lo, in_name)) { > + fuse_reply_err(req, EOPNOTSUPP); > + return; > + } > + > mapped_name = NULL; > name = in_name; > if (lo->xattrmap) { > @@ -3812,6 +3918,7 @@ int main(int argc, char *argv[]) > .allow_direct_io = 0, > .proc_self_fd = -1, > .user_killpriv_v2 = -1, > + .user_posix_acl = -1, > }; > struct lo_map_elem *root_elem; > struct lo_map_elem *reserve_elem; > @@ -3940,6 +4047,12 @@ int main(int argc, char *argv[]) > exit(1); > } > > + if (lo.user_posix_acl == 1 && !lo.xattr) { > + fuse_log(FUSE_LOG_ERR, "Can't enable posix ACLs. xattrs are disabled." > + "\n"); > + exit(1); > + } > + > lo.use_statx = true; > > se = fuse_session_new(&args, &lo_oper, sizeof(lo_oper), &lo); > -- > 2.25.4 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK