From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 01FD53214; Thu, 15 Aug 2024 14:38:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723732703; cv=none; b=m8AgpmlnglmXMCjhu6YEx3QcV/EWP7eW7kEkmbSOKrEGTMDY+GTsLXXq0Dxo24M974A00K/rM1OZHsD9iL5cZroy/KtsbdiTFoL2ITRmJXn1vVmLJqCVy50ptHnVuYZTgAKeBDXbFmHGG1jgNHWJK9ZwToTlKzWrtrERCWm1pPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723732703; c=relaxed/simple; bh=SEZeZcGDfxufyOpqQDNSoebr1aSptnBMhVa61sr83ss=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PzLOJHYXbBVp0PAojSoHqt4ynR1rMQmUXTgqr7mmnt0SpesEYcF08DX1zC5WYPQsDtZBPlt9GR/c3uSR2rDdmlqX09EIYxhAMhhOrQEpVYN8PpMfcT3GaMW8JKvTSwvjVrGoo8xJ0MP5pyUuxHJwsmGpyZvSOKSFkebzCfxBBO8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=k4S/LXyJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="k4S/LXyJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65E88C32786; Thu, 15 Aug 2024 14:38:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723732702; bh=SEZeZcGDfxufyOpqQDNSoebr1aSptnBMhVa61sr83ss=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k4S/LXyJqmFk/XT2b/zq4ZJ5IQTUU9grNNb0rxJL9efLyBWWg7BzxbSWiu3pTfGQI gEonbAGZU+wESs1l82HyBUIFpoD+SIJphGVVbw1w+WG/BcO6dHBS+0BK1v54rmNDmX YTcM2TtithjBEd3wIMA0iVIaakVb/5aNAEWbKhBk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Paul E. McKenney" , Marco Elver , Andrey Konovalov , kasan-dev@googlegroups.com, Sasha Levin Subject: [PATCH 5.10 261/352] rcutorture: Fix rcu_torture_fwd_cb_cr() data race Date: Thu, 15 Aug 2024 15:25:27 +0200 Message-ID: <20240815131929.532094273@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240815131919.196120297@linuxfoundation.org> References: <20240815131919.196120297@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul E. McKenney [ Upstream commit 6040072f4774a575fa67b912efe7722874be337b ] On powerpc systems, spinlock acquisition does not order prior stores against later loads. This means that this statement: rfcp->rfc_next = NULL; Can be reordered to follow this statement: WRITE_ONCE(*rfcpp, rfcp); Which is then a data race with rcu_torture_fwd_prog_cr(), specifically, this statement: rfcpn = READ_ONCE(rfcp->rfc_next) KCSAN located this data race, which represents a real failure on powerpc. Signed-off-by: Paul E. McKenney Acked-by: Marco Elver Cc: Andrey Konovalov Cc: Signed-off-by: Sasha Levin --- kernel/rcu/rcutorture.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 9f505688291e5..5c4bdbe76df04 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1867,7 +1867,7 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) spin_lock_irqsave(&rfp->rcu_fwd_lock, flags); rfcpp = rfp->rcu_fwd_cb_tail; rfp->rcu_fwd_cb_tail = &rfcp->rfc_next; - WRITE_ONCE(*rfcpp, rfcp); + smp_store_release(rfcpp, rfcp); WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1); i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV)); if (i >= ARRAY_SIZE(rfp->n_launders_hist)) -- 2.43.0