From patchwork Thu Apr 14 13:10:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 561611 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 39E13C38161 for ; Thu, 14 Apr 2022 14:01:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244630AbiDNN7f (ORCPT ); Thu, 14 Apr 2022 09:59:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344606AbiDNNuh (ORCPT ); Thu, 14 Apr 2022 09:50:37 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A74D220CE; Thu, 14 Apr 2022 06:44:26 -0700 (PDT) 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 A29D261BA7; Thu, 14 Apr 2022 13:44:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B70CAC385A1; Thu, 14 Apr 2022 13:44:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649943865; bh=1otHa4yN/axEC9FdbTD7iC+Jxt5hndq4z4yHEZtKmIs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LuJIvgjQRvp1AE65i+wfLhPL7Ml8O/IR/ZWylL6Nfneotb1CKY5wW58YrpA0T7YjF x4RvJ8UNbtTF1p6VbgJvQIiv10NnJEu42Mu61PHezWmJ88ihYDus0AeUk1VqHvuM95 wYay5X2nKbx5mV3nUMHMTfGfexSzerre/KcaaqI8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Duoming Zhou , Lin Ma , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 269/475] net/x25: Fix null-ptr-deref caused by x25_disconnect Date: Thu, 14 Apr 2022 15:10:54 +0200 Message-Id: <20220414110902.634519164@linuxfoundation.org> X-Mailer: git-send-email 2.35.2 In-Reply-To: <20220414110855.141582785@linuxfoundation.org> References: <20220414110855.141582785@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Duoming Zhou [ Upstream commit 7781607938c8371d4c2b243527430241c62e39c2 ] When the link layer is terminating, x25->neighbour will be set to NULL in x25_disconnect(). As a result, it could cause null-ptr-deref bugs in x25_sendmsg(),x25_recvmsg() and x25_connect(). One of the bugs is shown below. (Thread 1) | (Thread 2) x25_link_terminated() | x25_recvmsg() x25_kill_by_neigh() | ... x25_disconnect() | lock_sock(sk) ... | ... x25->neighbour = NULL //(1) | ... | x25->neighbour->extended //(2) The code sets NULL to x25->neighbour in position (1) and dereferences x25->neighbour in position (2), which could cause null-ptr-deref bug. This patch adds lock_sock() in x25_kill_by_neigh() in order to synchronize with x25_sendmsg(), x25_recvmsg() and x25_connect(). What`s more, the sock held by lock_sock() is not NULL, because it is extracted from x25_list and uses x25_list_lock to synchronize. Fixes: 4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect") Signed-off-by: Duoming Zhou Reviewed-by: Lin Ma Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/x25/af_x25.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index d8d603aa4887..c94aa587e0c9 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -1767,10 +1767,15 @@ void x25_kill_by_neigh(struct x25_neigh *nb) write_lock_bh(&x25_list_lock); - sk_for_each(s, &x25_list) - if (x25_sk(s)->neighbour == nb) + sk_for_each(s, &x25_list) { + if (x25_sk(s)->neighbour == nb) { + write_unlock_bh(&x25_list_lock); + lock_sock(s); x25_disconnect(s, ENETUNREACH, 0, 0); - + release_sock(s); + write_lock_bh(&x25_list_lock); + } + } write_unlock_bh(&x25_list_lock); /* Remove any related forwards */