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 55D3B187324; Mon, 12 Aug 2024 16:14:27 +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=1723479267; cv=none; b=ILkDbApuSqI7+iDl4Jnyjh6I1L0thzfdp5YSayXnvhcqgMpMXjV/Z3+O4UW6MbaLviCGrWlcXyRJ5nw1oPuae4Ryae1w2E+kTCIYYPu33taBZWBbxc1AU60qU5Fs/93LLW5lO+pPp+sSHEi1uTMqcRKvat7hTTA2boPXS1LBFQI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723479267; c=relaxed/simple; bh=FSziw1JsyI0mBiZnrpdDY8YJvxbSMf9F4yvAd+qaB00=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kGOsd+RVfFPEinWHdJ46BhhixOruWfiDE4RYVHBM3N4e3bF7iUVnzhvEC6s8RUMWDyh+pmXW/p9B+AKwGl3HzuVQVHEpd5GS7fdDdKxNQBLAQ+3EHUb/ULW7FJXPbdZJfHuxSv46IOuFioGKepBQWzCg1WxJ/x/+gxNHrmyY5kI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eoUczXA0; 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="eoUczXA0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC7F6C32782; Mon, 12 Aug 2024 16:14:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723479267; bh=FSziw1JsyI0mBiZnrpdDY8YJvxbSMf9F4yvAd+qaB00=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eoUczXA0cPrGT80T7oOGnhUIH1jAgvKGidGjvqWWuM+nYNNjGWgLP8b4l/StleznE lQcc0AD0x8NMa3ivfmSJZErYU/e2rDAT3/JJ9HC9oltIDHvasL2q5sQkwyUSbYEps9 615jeI29SOw11WslK+9dO1r+ZGfiG5xRODDkk2iU= 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 6.6 026/189] rcutorture: Fix rcu_torture_fwd_cb_cr() data race Date: Mon, 12 Aug 2024 18:01:22 +0200 Message-ID: <20240812160133.152514634@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240812160132.135168257@linuxfoundation.org> References: <20240812160132.135168257@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 6.6-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 781146600aa49..46612fb15fc6d 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2592,7 +2592,7 @@ 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