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 79B56C4332F for ; Fri, 11 Nov 2022 07:32:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232913AbiKKHcJ (ORCPT ); Fri, 11 Nov 2022 02:32:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232778AbiKKHcH (ORCPT ); Fri, 11 Nov 2022 02:32:07 -0500 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61F355B599 for ; Thu, 10 Nov 2022 23:32:06 -0800 (PST) Received: by mail-pj1-x104a.google.com with SMTP id m2-20020a17090a730200b0021020cce6adso4945807pjk.3 for ; Thu, 10 Nov 2022 23:32:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=d0z4ZqOjCKmXyUs7iMz5v/b1E02qlP3LIlnJ4q8w9/A=; b=M2IwOqcnfMwLGJzeNATGonrvMokklJg6m4PkurdIvL6eESyXf/bcAb1uGW/mTJusqJ 3ym30/nIwEo8rDGbooAue+HnPKoZcRPTQL0MJQC44VC3GwzMrF0NF0UR+H2JzrnZCZy+ 1FXb04DEx8lTBuF2ZOQBQL9qDFze3rmI3uQ0tyd52Uwjuu3aTPZhMkt/PUx9TR6jZZTA M3L1Xot34AO8kq5MIPWtN5YKvbXEcrJOniRATzYR5z0s44Y4/edXXWGq9loQzJfsJL9/ 1z2znHxCGZrY+xOeIV4X3AkMiAGi7bXDw3T5KBPVjsFE7Fov9RQCMTu7eEqjJk60dIdO sBYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=d0z4ZqOjCKmXyUs7iMz5v/b1E02qlP3LIlnJ4q8w9/A=; b=O5M9dhcGerAyCEz9RaNB8DVBUABscPg/3n/ntOruGvw301kAgW2OXjWWUgU4O2b4wM mZAwJrsUCW/RDMP4+OM8l3QZ2aab4qNSIlPl9bqclUPzVqMMMTYS6FEkCoh6iF8OyAfZ Pt2ZvKVWPy4QvpTSP/fC8G+kXI+G61mgqmWZlN0cXen64J0hUB+T0kYVwGybl1GTdVgH DUmIYwsglWSrSG4oEv1zmv0doI1PjfxvNz6LKTrzm2d+MEFrxdSiqOscqmknj4ch9CHL YHZu+4FSW546uga5dshbBQmf6PxuRsA64i+ifeu7W4wQDfw+fW5F7KSyY/+IgiO30oBP 3+bw== X-Gm-Message-State: ANoB5pmb27C57Eb8h2TRgb45AUeR2ZtIN39X086rZ148kw6cBQQBx8y5 vlV7U2yzbranNgOitQTO0bXXtA3dgvs= X-Google-Smtp-Source: AA0mqf610DQIjF+O0DgqpzNYgYex1vf8d0ahdx+2NgJAd3e7xYmyU5YHtBQTIoTtXiwW8BokTUSi4CrnnpE= X-Received: from avagin.kir.corp.google.com ([2620:0:1008:11:8cf3:f53:2863:82a3]) (user=avagin job=sendgmr) by 2002:aa7:93b3:0:b0:56a:af55:629c with SMTP id x19-20020aa793b3000000b0056aaf55629cmr1351902pff.82.1668151925950; Thu, 10 Nov 2022 23:32:05 -0800 (PST) Date: Thu, 10 Nov 2022 23:31:50 -0800 In-Reply-To: <20221111073154.784261-1-avagin@google.com> Mime-Version: 1.0 References: <20221111073154.784261-1-avagin@google.com> X-Mailer: git-send-email 2.38.1.493.g58b659f92b-goog Message-ID: <20221111073154.784261-2-avagin@google.com> Subject: [PATCH 1/5] seccomp: don't use semaphore and wait_queue together From: Andrei Vagin To: Kees Cook , Peter Zijlstra , Christian Brauner Cc: linux-kernel@vger.kernel.org, Andrei Vagin , Andy Lutomirski , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Peter Oskolkov , Tycho Andersen , Will Drewry , Vincent Guittot Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrei Vagin The main reason is to use new wake_up helpers that will be added in the following patches. But here are a few other reasons: * if we use two different ways, we always need to call them both. This patch fixes seccomp_notify_recv where we forgot to call wake_up_poll in the error path. * If we use one primitive, we can control how many waiters are woken up for each request. Our goal is to wake up just one that will handle a request. Right now, wake_up_poll can wake up one waiter and up(&match->notif->request) can wake up one more. Signed-off-by: Andrei Vagin --- kernel/seccomp.c | 41 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 36 insertions(+), 5 deletions(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index e9852d1b4a5e..876022e9c88c 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -145,7 +145,7 @@ struct seccomp_kaddfd { * @notifications: A list of struct seccomp_knotif elements. */ struct notification { - struct semaphore request; + atomic_t requests; u64 next_id; struct list_head notifications; }; @@ -1116,7 +1116,7 @@ static int seccomp_do_user_notification(int this_syscall, list_add_tail(&n.list, &match->notif->notifications); INIT_LIST_HEAD(&n.addfd); - up(&match->notif->request); + atomic_add(1, &match->notif->requests); wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM); /* @@ -1450,6 +1450,37 @@ find_notification(struct seccomp_filter *filter, u64 id) return NULL; } +static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync, + void *key) +{ + /* Avoid a wakeup if event not interesting for us. */ + if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR))) + return 0; + return autoremove_wake_function(wait, mode, sync, key); +} + +static int recv_wait_event(struct seccomp_filter *filter) +{ + DEFINE_WAIT_FUNC(wait, recv_wake_function); + int ret; + + if (atomic_add_unless(&filter->notif->requests, -1, 0) != 0) + return 0; + + for (;;) { + ret = prepare_to_wait_event(&filter->wqh, &wait, TASK_INTERRUPTIBLE); + + if (atomic_add_unless(&filter->notif->requests, -1, 0) != 0) + break; + + if (ret) + return ret; + + schedule(); + } + finish_wait(&filter->wqh, &wait); + return 0; +} static long seccomp_notify_recv(struct seccomp_filter *filter, void __user *buf) @@ -1467,7 +1498,7 @@ static long seccomp_notify_recv(struct seccomp_filter *filter, memset(&unotif, 0, sizeof(unotif)); - ret = down_interruptible(&filter->notif->request); + ret = recv_wait_event(filter); if (ret < 0) return ret; @@ -1515,7 +1546,8 @@ static long seccomp_notify_recv(struct seccomp_filter *filter, if (should_sleep_killable(filter, knotif)) complete(&knotif->ready); knotif->state = SECCOMP_NOTIFY_INIT; - up(&filter->notif->request); + atomic_add(1, &filter->notif->requests); + wake_up_poll(&filter->wqh, EPOLLIN | EPOLLRDNORM); } mutex_unlock(&filter->notify_lock); } @@ -1777,7 +1809,6 @@ static struct file *init_listener(struct seccomp_filter *filter) if (!filter->notif) goto out; - sema_init(&filter->notif->request, 0); filter->notif->next_id = get_random_u64(); INIT_LIST_HEAD(&filter->notif->notifications); -- 2.38.1.493.g58b659f92b-goog