From patchwork Thu Sep 16 08:40:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hanna Czenczek X-Patchwork-Id: 12498283 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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 43D2AC433EF for ; Thu, 16 Sep 2021 08:44:58 +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 0F05961209 for ; Thu, 16 Sep 2021 08:44:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0F05961209 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:46974 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mQn0r-0001JU-1r for qemu-devel@archiver.kernel.org; Thu, 16 Sep 2021 04:44:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48132) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQmxI-0004R2-UN for qemu-devel@nongnu.org; Thu, 16 Sep 2021 04:41:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:40801) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mQmxG-0004BU-0u for qemu-devel@nongnu.org; Thu, 16 Sep 2021 04:41:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631781673; 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=/LNdYWdfE7B711WCrLYvyDud7WHfFEqV3dUEWIbBA+E=; b=PjPV9i318SagWAZUs2jMKq0AwDgVXOHmqidGgUc0E4E3c2EP4b9FB42SNE4X8fqWvWCxYP xERrfmbutx6zviiTjVuYNqUbUs6c4Ta7pJ7qLTcN2XwommDsfr23uNG1NCMqyR2UqD7InR ihkqzxkwWugaYUwcOhD4ybJwGKhtmwg= 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-371-rXVcPl1FOM6oBR-XnebC4Q-1; Thu, 16 Sep 2021 04:41:12 -0400 X-MC-Unique: rXVcPl1FOM6oBR-XnebC4Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7D79E81451E for ; Thu, 16 Sep 2021 08:41:11 +0000 (UTC) Received: from localhost (unknown [10.39.192.150]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0462819736; Thu, 16 Sep 2021 08:41:03 +0000 (UTC) From: Hanna Reitz To: qemu-devel@nongnu.org, virtio-fs@redhat.com Subject: [PATCH v4 02/12] virtiofsd: Limit setxattr()'s creds-dropped region Date: Thu, 16 Sep 2021 10:40:35 +0200 Message-Id: <20210916084045.31684-3-hreitz@redhat.com> In-Reply-To: <20210916084045.31684-1-hreitz@redhat.com> References: <20210916084045.31684-1-hreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=hreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=hreitz@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=-0.39, 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_H2=-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: Hanna Reitz , Stefan Hajnoczi , "Dr . David Alan Gilbert" , Vivek Goyal Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" We only need to drop/switch our credentials for the (f)setxattr() call alone, not for the openat() or fchdir() around it. (Right now, this may not be that big of a problem, but with inodes being identified by file handles instead of an O_PATH fd, we will need open_by_handle_at() calls here, which is really fickle when it comes to credentials being dropped.) Signed-off-by: Hanna Reitz --- tools/virtiofsd/passthrough_ll.c | 34 +++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 6511a6acb4..b43afdfbd3 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -3123,6 +3123,7 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, bool switched_creds = false; bool cap_fsetid_dropped = false; struct lo_cred old = {}; + bool changed_cwd = false; if (block_xattr(lo, in_name)) { fuse_reply_err(req, EOPNOTSUPP); @@ -3158,6 +3159,24 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, ", name=%s value=%s size=%zd)\n", ino, name, value, size); sprintf(procname, "%i", inode->fd); + /* + * We can only open regular files or directories. If the inode is + * something else, we have to enter /proc/self/fd and use + * setxattr() on the link's filename there. + */ + if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) { + fd = openat(lo->proc_self_fd, procname, O_RDONLY); + if (fd < 0) { + saverr = errno; + goto out; + } + } else { + /* fchdir should not fail here */ + FCHDIR_NOFAIL(lo->proc_self_fd); + /* Set flag so the clean-up path will chdir back */ + changed_cwd = true; + } + /* * If we are setting posix access acl and if SGID needs to be * cleared, then switch to caller's gid and drop CAP_FSETID @@ -3178,20 +3197,12 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, } switched_creds = true; } - if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) { - fd = openat(lo->proc_self_fd, procname, O_RDONLY); - if (fd < 0) { - saverr = errno; - goto out; - } + if (fd >= 0) { ret = fsetxattr(fd, name, value, size, flags); saverr = ret == -1 ? errno : 0; } else { - /* fchdir should not fail here */ - FCHDIR_NOFAIL(lo->proc_self_fd); ret = setxattr(procname, name, value, size, flags); saverr = ret == -1 ? errno : 0; - FCHDIR_NOFAIL(lo->root.fd); } if (switched_creds) { if (cap_fsetid_dropped) @@ -3201,6 +3212,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, } out: + if (changed_cwd) { + /* Change CWD back, fchdir should not fail here */ + FCHDIR_NOFAIL(lo->root.fd); + } + if (fd >= 0) { close(fd); }