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[2620:137:e000::1:20]) by mx.google.com with ESMTP id z9-20020a056a001d8900b0057a7b003c82si3551976pfw.219.2023.01.24.15.45.42; Tue, 24 Jan 2023 15:45:54 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20210112 header.b="hTF/rOOw"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233911AbjAXXmI (ORCPT + 99 others); Tue, 24 Jan 2023 18:42:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233425AbjAXXmF (ORCPT ); Tue, 24 Jan 2023 18:42:05 -0500 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C8B0366AD for ; Tue, 24 Jan 2023 15:42:04 -0800 (PST) Received: by mail-pf1-x449.google.com with SMTP id 74-20020a62184d000000b0058b9f769609so7372490pfy.3 for ; Tue, 24 Jan 2023 15:42:04 -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=xszjUWrkTFV6nH5PVQmd1FHGHVSzRQgiwaL4b/IJnWk=; b=hTF/rOOwLOSId0uqhOxiwPXbw3/AXfGx+3kN23wQ14X/2W7FixnuFbx/Tx6JHDwQXz 3tP7WJa3k/2ZilKHOpQmLQ1aPQtsM6W9ZA44Ye/92hWta06p1j2LWKloC6IG/F0H5ZTj TSgVAaQ1+Dgfvq2UI3a2IcCw8yhkZnCGzpV6jAgfi5esnr30KxmO6iI7tMPSb6Fzs6wC 0DHDbnkKfA9g+2tJSzW3M8WBpev21WzZWhWbNoleSeuJDiZ4lODqxa/uxyIJDpNP6qTk Zw3YnweayXtLDiSYst8UKW40KJrsZUQaKb+QbMjDzz5SyjXSJHfHBR/6AHW8wSPOZLsF z8Uw== 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=xszjUWrkTFV6nH5PVQmd1FHGHVSzRQgiwaL4b/IJnWk=; b=iNex4cZgj1gCwN1Mf+P9byUJnGinw/vpWLrAB8c/qRCWV7gC5LnUSbLzb8gBGV0fo5 24Zla62fcp1zrK+lradpRYftOAnS1kxrKQVRdXK+txYHcK83dc17YktIGmRhs6+VXbw0 DOHp322oqsrL3hD51rNkXti3/EMRJSzN3PHiqUOHj+pajSRP1/5nt+Q6NCQoNlGUpnwt bkSW/UYabeHfzlLEQnJ/Mfe8DxMJNRz5t3HhHls7a8PRwxLER4xsWe6wsYzVkIpt4B3Z H/m4616nHsIIkHVqn71ODKjWLEmK71rz3CQsPdYLUKltCOHOTK1jNcP1q2F/5Lq8YuoL XMzA== X-Gm-Message-State: AFqh2kqzwZWup5tLn2cH/smiMXJMxgyL8At+nLU8Hzp6LNFF37ea6dKh 8vNPxvmpBJTiF3UU9XCOyx2xPR+GsM4= X-Received: from avagin.kir.corp.google.com ([2620:0:1008:11:cf1b:2f7f:3ca1:6488]) (user=avagin job=sendgmr) by 2002:a62:1c86:0:b0:58d:a84a:190b with SMTP id c128-20020a621c86000000b0058da84a190bmr3121261pfc.48.1674603723879; Tue, 24 Jan 2023 15:42:03 -0800 (PST) Date: Tue, 24 Jan 2023 15:41:51 -0800 In-Reply-To: <20230124234156.211569-1-avagin@google.com> Mime-Version: 1.0 References: <20230124234156.211569-1-avagin@google.com> X-Mailer: git-send-email 2.39.1.405.gd4c25cc71f-goog Message-ID: <20230124234156.211569-2-avagin@google.com> Subject: [PATCH 1/6] seccomp: don't use semaphore and wait_queue together From: Andrei Vagin To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Kees Cook , Christian Brauner , Chen Yu , Andrei Vagin , Andy Lutomirski , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Peter Oskolkov , Tycho Andersen , Will Drewry , Vincent Guittot X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1755949516008943197?= X-GMAIL-MSGID: =?utf-8?q?1755949516008943197?= 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);