From patchwork Wed Mar 23 16:01:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Michal_Koutn=C3=BD?= X-Patchwork-Id: 553893 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3740C433FE for ; Wed, 23 Mar 2022 16:01:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238325AbiCWQCv (ORCPT ); Wed, 23 Mar 2022 12:02:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238299AbiCWQCr (ORCPT ); Wed, 23 Mar 2022 12:02:47 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72EF17B12D for ; Wed, 23 Mar 2022 09:01:17 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 2BA76210DE; Wed, 23 Mar 2022 16:01:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1648051276; h=from:from:reply-to: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=tqDXuAMHxMddaOrZWSa7fljzAEyL5yzhIigHi3Xxj2Y=; b=L3ostfkylfaeRyMWD/+eGS0JSDkvXU2lwQI2NGgkK+iyS8YU0WFETD6vc1KZJY7OI70+5z +FtmcK8eOA4/u+qdZTaUNKtcr/dIU0+fFjrxVkwNRMthfIt0oFmUWQs8Tt9eNSzfdImEyY alJkYg7w8kdLq6dfKSqFXUE5P5HDPjY= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 02E2412FC5; Wed, 23 Mar 2022 16:01:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id CFIVO0tEO2KvegAAMHmgww (envelope-from ); Wed, 23 Mar 2022 16:01:15 +0000 From: =?utf-8?q?Michal_Koutn=C3=BD?= To: gregkh@linuxfoundation.org Cc: masami.ichikawa@cybertrust.co.jp, mkoutny@suse.com, stable@vger.kernel.org, tj@kernel.org Subject: [PATCH 3/3] cgroup-v1: Correct privileges check in release_agent writes Date: Wed, 23 Mar 2022 17:01:02 +0100 Message-Id: <20220323160102.3347-3-mkoutny@suse.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220323160102.3347-1-mkoutny@suse.com> References: <20220323160102.3347-1-mkoutny@suse.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org commit 467a726b754f474936980da793b4ff2ec3e382a7 upstream. The idea is to check: a) the owning user_ns of cgroup_ns, b) capabilities in init_user_ns. The commit 24f600856418 ("cgroup-v1: Require capabilities to set release_agent") got this wrong in the write handler of release_agent since it checked user_ns of the opener (may be different from the owning user_ns of cgroup_ns). Secondly, to avoid possibly confused deputy, the capability of the opener must be checked. Fixes: 24f600856418 ("cgroup-v1: Require capabilities to set release_agent") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/stable/20220216121142.GB30035@blackbody.suse.cz/ Signed-off-by: Michal Koutný Reviewed-by: Masami Ichikawa(CIP) Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup-v1.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 40b8d4e4a810..8f0ea12d7cee 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -544,6 +544,7 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { struct cgroup *cgrp; + struct cgroup_file_ctx *ctx; BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); @@ -551,8 +552,9 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, * Release agent gets called with all capabilities, * require capabilities to set release agent. */ - if ((of->file->f_cred->user_ns != &init_user_ns) || - !capable(CAP_SYS_ADMIN)) + ctx = of->priv; + if ((ctx->ns->user_ns != &init_user_ns) || + !file_ns_capable(of->file, &init_user_ns, CAP_SYS_ADMIN)) return -EPERM; cgrp = cgroup_kn_lock_live(of->kn, false);