From patchwork Fri Jul 30 15:01:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Max Reitz X-Patchwork-Id: 12411495 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 9177EC4338F for ; Fri, 30 Jul 2021 15:04:32 +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 5201660F46 for ; Fri, 30 Jul 2021 15:04:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 5201660F46 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]:54848 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m9U3q-00085G-E5 for qemu-devel@archiver.kernel.org; Fri, 30 Jul 2021 11:04:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49184) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m9U29-0005Xg-UE for qemu-devel@nongnu.org; Fri, 30 Jul 2021 11:02:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:41323) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m9U27-0007n0-QJ for qemu-devel@nongnu.org; Fri, 30 Jul 2021 11:02:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1627657362; 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=l/mIIgvz3twLcuTXGIRgLgYVjiXbPrPC8d+/bqE4twI=; b=cUDX+75mqJnLrEmIpOtROTGOZjhfgYIIgQhzLj7qd7LuX4dfl5L8Jai2oY74DZvHLomqQX FNm201lLJ8mXQsgOfkmGXmxVSQpToSZTdG1//jpAuhwWA6VqlMO0CiAOVKGKMkNdzrs20c jqkV/4drp7mXBRWG0yehqm+2ENVqWTw= 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-545-pDd-DK7UO_CbdOS6kgOohQ-1; Fri, 30 Jul 2021 11:02:41 -0400 X-MC-Unique: pDd-DK7UO_CbdOS6kgOohQ-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 7A48083DC1D for ; Fri, 30 Jul 2021 15:01:46 +0000 (UTC) Received: from localhost (unknown [10.39.193.62]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1819A5D9CA; Fri, 30 Jul 2021 15:01:45 +0000 (UTC) From: Max Reitz To: qemu-devel@nongnu.org, virtio-fs@redhat.com Subject: [PATCH v3 01/10] virtiofsd: Limit setxattr()'s creds-dropped region Date: Fri, 30 Jul 2021 17:01:25 +0200 Message-Id: <20210730150134.216126-2-mreitz@redhat.com> In-Reply-To: <20210730150134.216126-1-mreitz@redhat.com> References: <20210730150134.216126-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.717, 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_H3=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: Stefan Hajnoczi , "Dr . David Alan Gilbert" , Vivek Goyal , Max Reitz 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: Max 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 38b2af8599..1f27eeabc5 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -3121,6 +3121,7 @@ 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 open_inode; if (block_xattr(lo, in_name)) { fuse_reply_err(req, EOPNOTSUPP); @@ -3155,7 +3156,24 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, fuse_log(FUSE_LOG_DEBUG, "lo_setxattr(ino=%" PRIu64 ", name=%s value=%s size=%zd)\n", ino, name, value, size); + /* + * 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. + */ + open_inode = S_ISREG(inode->filetype) || S_ISDIR(inode->filetype); sprintf(procname, "%i", inode->fd); + if (open_inode) { + 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); + } + /* * If we are setting posix access acl and if SGID needs to be * cleared, then switch to caller's gid and drop CAP_FSETID @@ -3176,20 +3194,13 @@ 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 (open_inode) { + assert(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) @@ -3198,6 +3209,11 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name, lo_restore_cred(&old, false); } + if (!open_inode) { + /* Change CWD back, fchdir should not fail here */ + FCHDIR_NOFAIL(lo->root.fd); + } + out: if (fd >= 0) { close(fd);