From mboxrd@z Thu Jan 1 00:00:00 1970 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 51124C35294 for ; Mon, 24 Jan 2022 23:05:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1842228AbiAXXBX (ORCPT ); Mon, 24 Jan 2022 18:01:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1573020AbiAXVzI (ORCPT ); Mon, 24 Jan 2022 16:55:08 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B284CC07E2AF; Mon, 24 Jan 2022 12:37:46 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 6EF23B81063; Mon, 24 Jan 2022 20:37:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F4D9C340E5; Mon, 24 Jan 2022 20:37:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643056664; bh=vNMezxssj6VcvR7r/jjQIM53BOA5+j+5fVwfrXZIJ98=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xQIaWVpxutPsC6GegXirRFVNxvAInucOp9zRZ7fWvZBtYIl2qFnakw9SfT6fmmQ+x e4W3moSeLmRzT4LPhOJ1h27iq56fxze3Wy8Nc4kkwVeYH0o92/rVD9c1QYWd3PSCQl KszC4l8ktf+N/gyFmRL/NZjAjzv9zF87dQezbiJM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Gaosheng Cui , Richard Guy Briggs , Paul Moore , Sasha Levin Subject: [PATCH 5.15 559/846] audit: ensure userspace is penalized the same as the kernel when under pressure Date: Mon, 24 Jan 2022 19:41:16 +0100 Message-Id: <20220124184120.310761403@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184100.867127425@linuxfoundation.org> References: <20220124184100.867127425@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paul Moore [ Upstream commit 8f110f530635af44fff1f4ee100ecef0bac62510 ] Due to the audit control mutex necessary for serializing audit userspace messages we haven't been able to block/penalize userspace processes that attempt to send audit records while the system is under audit pressure. The result is that privileged userspace applications have a priority boost with respect to audit as they are not bound by the same audit queue throttling as the other tasks on the system. This patch attempts to restore some balance to the system when under audit pressure by blocking these privileged userspace tasks after they have finished their audit processing, and dropped the audit control mutex, but before they return to userspace. Reported-by: Gaosheng Cui Tested-by: Gaosheng Cui Reviewed-by: Richard Guy Briggs Signed-off-by: Paul Moore Signed-off-by: Sasha Levin --- kernel/audit.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/kernel/audit.c b/kernel/audit.c index 4cebadb5f30db..eab7282668ab9 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1540,6 +1540,20 @@ static void audit_receive(struct sk_buff *skb) nlh = nlmsg_next(nlh, &len); } audit_ctl_unlock(); + + /* can't block with the ctrl lock, so penalize the sender now */ + if (audit_backlog_limit && + (skb_queue_len(&audit_queue) > audit_backlog_limit)) { + DECLARE_WAITQUEUE(wait, current); + + /* wake kauditd to try and flush the queue */ + wake_up_interruptible(&kauditd_wait); + + add_wait_queue_exclusive(&audit_backlog_wait, &wait); + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_timeout(audit_backlog_wait_time); + remove_wait_queue(&audit_backlog_wait, &wait); + } } /* Log information about who is connecting to the audit multicast socket */ @@ -1824,7 +1838,9 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, * task_tgid_vnr() since auditd_pid is set in audit_receive_msg() * using a PID anchored in the caller's namespace * 2. generator holding the audit_cmd_mutex - we don't want to block - * while holding the mutex */ + * while holding the mutex, although we do penalize the sender + * later in audit_receive() when it is safe to block + */ if (!(auditd_test_task(current) || audit_ctl_owner_current())) { long stime = audit_backlog_wait_time; -- 2.34.1