From patchwork Thu Dec 12 16:37:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Dr. David Alan Gilbert" X-Patchwork-Id: 11288673 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 719F0112B for ; Thu, 12 Dec 2019 17:04:17 +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 4820F214AF for ; Thu, 12 Dec 2019 17:04:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ww5r7BiO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4820F214AF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:34394 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ifRsu-0007fF-0f for patchwork-qemu-devel@patchwork.kernel.org; Thu, 12 Dec 2019 12:04:16 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:48027) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ifRVT-0005bj-6H for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:40:04 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ifRVR-0001sF-PL for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:40:03 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:32650 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ifRVR-0001r8-Kf for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:40:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576168801; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wqtSCXFgXvLFNuOOAFjEDf9T7WW4CC7I06u4+L0dcrY=; b=Ww5r7BiOK0uiEVv/OjJdoK8oE5IMlF7fG34hvX+FlTuvOAhrSA+DoHeBJFK6Pa0agmYKqZ 89z+h73yWp9Z10MKoY3GRsAE3/3+AuddOtP9Cz/NLPrWl/dXjvMjUf6ME1XuiqEuor2SsM w+KoWSvUa/hwzulLK2tPD4wRt1xQhOs= 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-322-xSd0SLKZNUC2Ry7Dri-QUg-1; Thu, 12 Dec 2019 11:39:59 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F1B37801E66 for ; Thu, 12 Dec 2019 16:39:58 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-226.ams2.redhat.com [10.36.116.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id 250A160BE1; Thu, 12 Dec 2019 16:39:57 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Subject: [PATCH 032/104] virtiofsd: passthrough_ll: create new files in caller's context Date: Thu, 12 Dec 2019 16:37:52 +0000 Message-Id: <20191212163904.159893-33-dgilbert@redhat.com> In-Reply-To: <20191212163904.159893-1-dgilbert@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: xSd0SLKZNUC2Ry7Dri-QUg-1 X-Mimecast-Spam-Score: 0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 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: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Vivek Goyal We need to create files in the caller's context. Otherwise after creating a file, the caller might not be able to do file operations on that file. Changed effective uid/gid to caller's uid/gid, create file and then switch back to uid/gid 0. Use syscall(setresuid, ...) otherwise glibc does some magic to change EUID in all threads, which is not what we want. Signed-off-by: Vivek Goyal Signed-off-by: Miklos Szeredi --- tools/virtiofsd/passthrough_ll.c | 79 ++++++++++++++++++++++++++++++-- 1 file changed, 74 insertions(+), 5 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 68bacb6fc5..0188cd9ad6 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -49,6 +49,7 @@ #include #include #include +#include #include #include @@ -83,6 +84,11 @@ struct lo_inode { uint64_t refcount; /* protected by lo->mutex */ }; +struct lo_cred { + uid_t euid; + gid_t egid; +}; + enum { CACHE_NEVER, CACHE_NORMAL, @@ -383,6 +389,52 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) } } +/* + * Change to uid/gid of caller so that file is created with + * ownership of caller. + * TODO: What about selinux context? + */ +static int lo_change_cred(fuse_req_t req, struct lo_cred *old) +{ + int res; + + old->euid = geteuid(); + old->egid = getegid(); + + res = syscall(SYS_setresgid, -1, fuse_req_ctx(req)->gid, -1); + if (res == -1) { + return errno; + } + + res = syscall(SYS_setresuid, -1, fuse_req_ctx(req)->uid, -1); + if (res == -1) { + int errno_save = errno; + + syscall(SYS_setresgid, -1, old->egid, -1); + return errno_save; + } + + return 0; +} + +/* Regain Privileges */ +static void lo_restore_cred(struct lo_cred *old) +{ + int res; + + res = syscall(SYS_setresuid, -1, old->euid, -1); + if (res == -1) { + fuse_log(FUSE_LOG_ERR, "seteuid(%u): %m\n", old->euid); + exit(1); + } + + res = syscall(SYS_setresgid, -1, old->egid, -1); + if (res == -1) { + fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid); + exit(1); + } +} + static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, const char *name, mode_t mode, dev_t rdev, const char *link) @@ -391,12 +443,21 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, int saverr; struct lo_inode *dir = lo_inode(req, parent); struct fuse_entry_param e; + struct lo_cred old = {}; saverr = ENOMEM; + saverr = lo_change_cred(req, &old); + if (saverr) { + goto out; + } + res = mknod_wrapper(dir->fd, name, link, mode, rdev); saverr = errno; + + lo_restore_cred(&old); + if (res == -1) { goto out; } @@ -794,26 +855,34 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name, struct lo_data *lo = lo_data(req); struct fuse_entry_param e; int err; + struct lo_cred old = {}; if (lo_debug(req)) { fuse_log(FUSE_LOG_DEBUG, "lo_create(parent=%" PRIu64 ", name=%s)\n", parent, name); } + err = lo_change_cred(req, &old); + if (err) { + goto out; + } + fd = openat(lo_fd(req, parent), name, (fi->flags | O_CREAT) & ~O_NOFOLLOW, mode); - if (fd == -1) { - return (void)fuse_reply_err(req, errno); - } + err = fd == -1 ? errno : 0; + lo_restore_cred(&old); - fi->fh = fd; + if (!err) { + fi->fh = fd; + err = lo_do_lookup(req, parent, name, &e); + } if (lo->cache == CACHE_NEVER) { fi->direct_io = 1; } else if (lo->cache == CACHE_ALWAYS) { fi->keep_cache = 1; } - err = lo_do_lookup(req, parent, name, &e); +out: if (err) { fuse_reply_err(req, err); } else {