From patchwork Tue Apr 25 18:49:05 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 87529 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp3617623vqo; Tue, 25 Apr 2023 12:14:41 -0700 (PDT) X-Google-Smtp-Source: AKy350Y2dnykNypesqjKTYpTM8dwkf4o5YvC3YuTohdDcYugbtuAX6yIR2HDGjJIr6uR5JTmv4Jb X-Received: by 2002:a17:902:bc47:b0:1a8:153a:99a4 with SMTP id t7-20020a170902bc4700b001a8153a99a4mr17929824plz.64.1682450081115; Tue, 25 Apr 2023 12:14:41 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1682450081; cv=none; d=google.com; s=arc-20160816; b=sk0CbLaef3QEhVcbqt+s06FoZ9ejZmRuQlnVZJ0VCkH24o1zwjjYOJlHCzGEsN+SDi MfO9zuNQ6o4XIOw+kD5wOAnaGS2gWfj6Ln3olkf2JmLK5xz+pnCuOP0yRENR5wmqqW1x Hx8NndPR6y5Un77vD6EPb+2YIZ//zF/GhrTrGopW3ISULjQc3TYeFaCuo7Iy0Ssewgun qsS9wWeUYLT+zz2z66IiqDMjGwtN56NkyHu0+RxsZTNO9yXLlIdES7DYv2tcvkBG7Zj/ yPnyNjE3y0zHp9zBNZedoNSntF/fr1PQfuNB0SZL/nuNmaAYeVtimwwuzchB3xi7/AAQ OPeA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:date:mime-version:references:subject:cc:to:from :dkim-signature:dkim-signature:message-id; bh=me0I7Ik/2QPR1Cxbi2+BttUOdfbhm4wKXX1mgySouMM=; b=sJUUdAV5QlkOxqSGWJQg1fvN2tzVO8tTYA7aBElLWTvn/OwbGvtHU7MfbDyrbrcnk/ S7wtVjqVMekr0y+U1wE5uxV7+2nkrYqRlcMuFZq4CdmaVB91JNT09Ae6F8bGF7E/KKmT e52eRb5fzTki7egPmDSCx6nTvZcHpSAOihrZ3aEf1VEyfyU8lc0XrM112yeyNnPbeVZd SJ7Hc0aFSSF/KG5EerYBhrx0Jn5MybAENOC3gGQuP5UyhDht8HfZPwFD0jldZsF7zXyL sBvvJdB3uHMtSLv+NK0vj/N+XR2hkJ+UftikTqBsRehtIgAxJ1TrjsNS/OFJBcCueQ02 wmKA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b="BZ/yP6Bs"; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b=GecTvQlK; 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=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id e15-20020a17090301cf00b001a6f0eab385si15741202plh.55.2023.04.25.12.14.26; Tue, 25 Apr 2023 12:14:41 -0700 (PDT) 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=@linutronix.de header.s=2020 header.b="BZ/yP6Bs"; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b=GecTvQlK; 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=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234809AbjDYSt2 (ORCPT + 99 others); Tue, 25 Apr 2023 14:49:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234683AbjDYStL (ORCPT ); Tue, 25 Apr 2023 14:49:11 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D12C916188 for ; Tue, 25 Apr 2023 11:49:06 -0700 (PDT) Message-ID: <20230425183313.143596887@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1682448545; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=me0I7Ik/2QPR1Cxbi2+BttUOdfbhm4wKXX1mgySouMM=; b=BZ/yP6BsoN6Kaono2yFEiQcD9foanNtBqch0FSIVVI7ewIsR2CtkITKpxKcAdGuAptLhEc bIHcVieXzzVpeJ5rG00ec5AyD8hzKv4rhzLlz0u1TpLucVTEGywLAv501vCuOUD59fi06L UxgpWTbGPyqJC6h2kET0SogqxEQ7WZj56KQ2oeT86f/iTrhXgbPdbKvq+iz8NGJx8dqHLc RH+/kF/vj0KkfA63z2OqdXmlLqVzgmJ43vg8442IMkjMytwWJ18j5IsvNHMGB39pTbwMx5 fNPsiDurCMxLhrXAstojRe/B4ATAXCciNan3Vys/w0GdraUakDCrAaEZEAbzbw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1682448545; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=me0I7Ik/2QPR1Cxbi2+BttUOdfbhm4wKXX1mgySouMM=; b=GecTvQlK3AjHVOha7Dld2H5pG/RjVzlGyVF9JQnFpRjNq5woiEBG2gQ+6/wkvMxpc6tDQi 0HM/7nptC6ZwZmDg== From: Thomas Gleixner To: LKML Cc: Frederic Weisbecker , Anna-Maria Behnsen , Peter Zijlstra , Sebastian Siewior , syzbot+5c54bd3eb218bb595aa9@syzkaller.appspotmail.com, Dmitry Vyukov , Michael Kerrisk Subject: [patch 06/20] posix-timers: Annotate concurrent access to k_itimer::it_signal References: <20230425181827.219128101@linutronix.de> MIME-Version: 1.0 Date: Tue, 25 Apr 2023 20:49:05 +0200 (CEST) X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED 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?1764176776152713218?= X-GMAIL-MSGID: =?utf-8?q?1764176776152713218?= k_itimer::it_signal is read lockless in the RCU protected hash lookup, but it can be written concurrently in the timer_create() and timer_delete() path. Annotate these places with READ_ONCE() and WRITE_ONCE() Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker --- kernel/time/posix-timers.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -109,9 +109,9 @@ static struct k_itimer *__posix_timers_f { struct k_itimer *timer; - hlist_for_each_entry_rcu(timer, head, t_hash, - lockdep_is_held(&hash_lock)) { - if ((timer->it_signal == sig) && (timer->it_id == id)) + hlist_for_each_entry_rcu(timer, head, t_hash, lockdep_is_held(&hash_lock)) { + /* timer->it_signal can be set concurrently */ + if ((READ_ONCE(timer->it_signal) == sig) && (timer->it_id == id)) return timer; } return NULL; @@ -557,7 +557,7 @@ static int do_timer_create(clockid_t whi spin_lock_irq(¤t->sighand->siglock); /* This makes the timer valid in the hash table */ - new_timer->it_signal = current->signal; + WRITE_ONCE(new_timer->it_signal, current->signal); list_add(&new_timer->list, ¤t->signal->posix_timers); spin_unlock_irq(¤t->sighand->siglock); @@ -1051,10 +1051,10 @@ SYSCALL_DEFINE1(timer_delete, timer_t, t list_del(&timer->list); spin_unlock(¤t->sighand->siglock); /* - * This keeps any tasks waiting on the spin lock from thinking - * they got something (see the lock code above). + * A concurrent lookup could check timer::it_signal lockless. It + * will reevaluate with timer::it_lock held and observe the NULL. */ - timer->it_signal = NULL; + WRITE_ONCE(timer->it_signal, NULL); unlock_timer(timer, flags); release_posix_timer(timer, IT_ID_SET);