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 81FFF20A5EE; Thu, 12 Dec 2024 17:39:44 +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=1734025184; cv=none; b=dQCxJpxRQOqXB9Pr2H+JjtJuVOwYsyYJZuNbn/rQbKuQjJB7lB82xNtJvWvlIW/A6LNu9PXllZGXVvLkWm4ybTXLoUuZYiZSwVaVKuImgFbt0o47sWQuSepirixKPsLqcH/ufRNHJHNFyEBh8l7HWM6iRtvJaNUoxfN2KCruSv8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734025184; c=relaxed/simple; bh=3H23y+nhAz9BuiyO6FHCQB15Dym9+QCrFh8NP/rdzA8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=g42/wORV+oaWFAAcUH+0YPe5PQZJn/zkZUjYAUv6wIwEa9l4eal5IPzAZ/BLsoFCH9VpTfIJPeuOU9ndBxtJC8QvKyB/TOMKkylRZHfDkjCDIw1y3zyVYPlQGFQj5ZeFc6Hnj+qFgNOVO6D/2RZS57pYh5wwFzg8P2foWo0gWJo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VHAswu22; 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="VHAswu22" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09AA8C4CECE; Thu, 12 Dec 2024 17:39:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734025184; bh=3H23y+nhAz9BuiyO6FHCQB15Dym9+QCrFh8NP/rdzA8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VHAswu22cbcsB2IKyX93EJPOhV6mVK53xuc3wXcU6x7mo7CbZRBM+GLAzAXS4jPqk ZhdVoOKtaQ8Vb695UxDFz0dsD9WM9JzNRZBKv1E6kIQllCjoq84MApYglTSXBK4CVA Y+G6yy3QcGBqv24TM7RmMcwdZ6lS1AloLafM/byA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Breno Leitao , Michal Kubiak , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.4 085/321] netpoll: Use rcu_access_pointer() in netpoll_poll_lock Date: Thu, 12 Dec 2024 16:00:03 +0100 Message-ID: <20241212144233.340015634@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241212144229.291682835@linuxfoundation.org> References: <20241212144229.291682835@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 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Breno Leitao [ Upstream commit a57d5a72f8dec7db8a79d0016fb0a3bdecc82b56 ] The ndev->npinfo pointer in netpoll_poll_lock() is RCU-protected but is being accessed directly for a NULL check. While no RCU read lock is held in this context, we should still use proper RCU primitives for consistency and correctness. Replace the direct NULL check with rcu_access_pointer(), which is the appropriate primitive when only checking for NULL without dereferencing the pointer. This function provides the necessary ordering guarantees without requiring RCU read-side protection. Fixes: bea3348eef27 ("[NET]: Make NAPI polling independent of struct net_device objects.") Signed-off-by: Breno Leitao Reviewed-by: Michal Kubiak Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-2-a1888dcb4a02@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- include/linux/netpoll.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h index 676f1ff161a98..3ff0303672842 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -78,7 +78,7 @@ static inline void *netpoll_poll_lock(struct napi_struct *napi) { struct net_device *dev = napi->dev; - if (dev && dev->npinfo) { + if (dev && rcu_access_pointer(dev->npinfo)) { int owner = smp_processor_id(); while (cmpxchg(&napi->poll_owner, -1, owner) != -1) -- 2.43.0