From patchwork Thu Jan 23 16:45:37 2020 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: 11349057 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 D2D261398 for ; Thu, 23 Jan 2020 19:06:49 +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 A81AA2077C for ; Thu, 23 Jan 2020 19:06:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Su6rzzDB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A81AA2077C 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]:35294 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iuhoW-0000OL-AV for patchwork-qemu-devel@patchwork.kernel.org; Thu, 23 Jan 2020 14:06:48 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41475) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iufeB-0005FK-16 for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:48:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iufe9-0006gY-Fo for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:58 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:24012 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iufe9-0006g6-Cb for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579798077; 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=pucqjnQfkQgODQBaQLuvW2l9M7uY/arYC5AvJoD6Bd0=; b=Su6rzzDB/T8yRcQYyLD+B1tdo7ZXuWo1sYecgazH34vtnhFLJvoRzrrgvQYOPyDXMsQanG YMya7jnvoLhmNp0O1hk0F5ciB/2KqHGB6XAXOTBC+qBiXAyTUnz8OmS7CtL0jsU2Ngi9Xu bVhYTw/X5VNx9aOL/yg/EstHiU8UEbE= 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-346-0Q1Q1o6bO8iJ8iRiIMAMpA-1; Thu, 23 Jan 2020 11:47:55 -0500 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 B5BF5190B2B5 for ; Thu, 23 Jan 2020 16:47:54 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-110.ams2.redhat.com [10.36.116.110]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0CD7819C69; Thu, 23 Jan 2020 16:47:53 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com Subject: [PULL 055/108] virtiofsd: Drop CAP_FSETID if client asked for it Date: Thu, 23 Jan 2020 16:45:37 +0000 Message-Id: <20200123164630.91498-56-dgilbert@redhat.com> In-Reply-To: <20200123164630.91498-1-dgilbert@redhat.com> References: <20200123164630.91498-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: 0Q1Q1o6bO8iJ8iRiIMAMpA-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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 If client requested killing setuid/setgid bits on file being written, drop CAP_FSETID capability so that setuid/setgid bits are cleared upon write automatically. pjdfstest chown/12.t needs this. Signed-off-by: Vivek Goyal dgilbert: reworked for libcap-ng Reviewed-by: Misono Tomohiro Reviewed-by: Sergio Lopez Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 105 +++++++++++++++++++++++++++++++ 1 file changed, 105 insertions(+) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 97e7c75667..d53cb1e005 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -201,6 +201,91 @@ static int load_capng(void) return 0; } +/* + * Helpers for dropping and regaining effective capabilities. Returns 0 + * on success, error otherwise + */ +static int drop_effective_cap(const char *cap_name, bool *cap_dropped) +{ + int cap, ret; + + cap = capng_name_to_capability(cap_name); + if (cap < 0) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n", + cap_name, strerror(errno)); + goto out; + } + + if (load_capng()) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "load_capng() failed\n"); + goto out; + } + + /* We dont have this capability in effective set already. */ + if (!capng_have_capability(CAPNG_EFFECTIVE, cap)) { + ret = 0; + goto out; + } + + if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, cap)) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "capng_update(DROP,) failed\n"); + goto out; + } + + if (capng_apply(CAPNG_SELECT_CAPS)) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "drop:capng_apply() failed\n"); + goto out; + } + + ret = 0; + if (cap_dropped) { + *cap_dropped = true; + } + +out: + return ret; +} + +static int gain_effective_cap(const char *cap_name) +{ + int cap; + int ret = 0; + + cap = capng_name_to_capability(cap_name); + if (cap < 0) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n", + cap_name, strerror(errno)); + goto out; + } + + if (load_capng()) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "load_capng() failed\n"); + goto out; + } + + if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, cap)) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "capng_update(ADD,) failed\n"); + goto out; + } + + if (capng_apply(CAPNG_SELECT_CAPS)) { + ret = errno; + fuse_log(FUSE_LOG_ERR, "gain:capng_apply() failed\n"); + goto out; + } + ret = 0; + +out: + return ret; +} + static void lo_map_init(struct lo_map *map) { map->elems = NULL; @@ -1577,6 +1662,7 @@ static void lo_write_buf(fuse_req_t req, fuse_ino_t ino, (void)ino; ssize_t res; struct fuse_bufvec out_buf = FUSE_BUFVEC_INIT(fuse_buf_size(in_buf)); + bool cap_fsetid_dropped = false; out_buf.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK; out_buf.buf[0].fd = lo_fi_fd(req, fi); @@ -1588,12 +1674,31 @@ static void lo_write_buf(fuse_req_t req, fuse_ino_t ino, out_buf.buf[0].size, (unsigned long)off); } + /* + * If kill_priv is set, drop CAP_FSETID which should lead to kernel + * clearing setuid/setgid on file. + */ + if (fi->kill_priv) { + res = drop_effective_cap("FSETID", &cap_fsetid_dropped); + if (res != 0) { + fuse_reply_err(req, res); + return; + } + } + res = fuse_buf_copy(&out_buf, in_buf); if (res < 0) { fuse_reply_err(req, -res); } else { fuse_reply_write(req, (size_t)res); } + + if (cap_fsetid_dropped) { + res = gain_effective_cap("FSETID"); + if (res) { + fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_FSETID\n"); + } + } } static void lo_statfs(fuse_req_t req, fuse_ino_t ino)