Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ECBB7C433F5 for ; Mon, 27 Dec 2021 15:36:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237862AbhL0Pgi (ORCPT ); Mon, 27 Dec 2021 10:36:38 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:36296 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238395AbhL0PgG (ORCPT ); Mon, 27 Dec 2021 10:36:06 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6EEAD610A2; Mon, 27 Dec 2021 15:36:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E75FC36AE7; Mon, 27 Dec 2021 15:36:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1640619364; bh=utJJp+4dkjOiOt7JYg3l69mAl/5bBtjW9glZwfKZvjE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LFqfUtGK2wXmirx58zbBHIW3vk0/XjCR01wte0mXLH/vYXgvjWjHCwE7qWT1tyubd KE6Aaup3nqXYO+SkwIhn7zTA8TJvCnc8i0NZA3bb/DBgeMmt/2Kni5AgSHnXGWaYht v+rsH4m3CwktoXNCl/HGW6dmylTtisfWoOi21DxE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hanjie Wu , Lin Ma , "David S. Miller" Subject: [PATCH 5.4 44/47] ax25: NPD bug when detaching AX25 device Date: Mon, 27 Dec 2021 16:31:20 +0100 Message-Id: <20211227151322.322661674@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211227151320.801714429@linuxfoundation.org> References: <20211227151320.801714429@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lin Ma commit 1ade48d0c27d5da1ccf4b583d8c5fc8b534a3ac8 upstream. The existing cleanup routine implementation is not well synchronized with the syscall routine. When a device is detaching, below race could occur. static int ax25_sendmsg(...) { ... lock_sock() ax25 = sk_to_ax25(sk); if (ax25->ax25_dev == NULL) // CHECK ... ax25_queue_xmit(skb, ax25->ax25_dev->dev); // USE ... } static void ax25_kill_by_device(...) { ... if (s->ax25_dev == ax25_dev) { s->ax25_dev = NULL; ... } Other syscall functions like ax25_getsockopt, ax25_getname, ax25_info_show also suffer from similar races. To fix them, this patch introduce lock_sock() into ax25_kill_by_device in order to guarantee that the nullify action in cleanup routine cannot proceed when another socket request is pending. Signed-off-by: Hanjie Wu Signed-off-by: Lin Ma Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ax25/af_ax25.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -85,8 +85,10 @@ static void ax25_kill_by_device(struct n again: ax25_for_each(s, &ax25_list) { if (s->ax25_dev == ax25_dev) { - s->ax25_dev = NULL; spin_unlock_bh(&ax25_list_lock); + lock_sock(s->sk); + s->ax25_dev = NULL; + release_sock(s->sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock);