From patchwork Mon Jan 24 18:32:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 535895 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 AB59FC43219 for ; Mon, 24 Jan 2022 20:13:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240082AbiAXUN5 (ORCPT ); Mon, 24 Jan 2022 15:13:57 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:53466 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354946AbiAXULy (ORCPT ); Mon, 24 Jan 2022 15:11:54 -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 ams.source.kernel.org (Postfix) with ESMTPS id DD6AAB81257; Mon, 24 Jan 2022 20:11:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1AB71C340E5; Mon, 24 Jan 2022 20:11:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643055110; bh=DJ/cYkr8MzqT7hAfv92BLVMqYFrXoXo4x8FHMhWFLhY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I+jvyW6/bWexe5YdhhFq4oMajWt4gfUGTWdCUHqThjQR1WjxAx+7UE5sPplLGdjfx QB3g27fqBW4ofpY1nCpphH53ceGcY1kjTZMhSScl/Ar+NcgW1YsWl0YgOBNvQqWNaE Y7FR1WqcBcwbqc/tqncbgNZG4dXfxk6gyjLX8qhg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Krzysztof Kozlowski , "David S. Miller" , syzbot+7f23bcddf626e0593a39@syzkaller.appspotmail.com Subject: [PATCH 5.15 012/846] nfc: llcp: fix NULL error pointer dereference on sendmsg() after failed bind() Date: Mon, 24 Jan 2022 19:32:09 +0100 Message-Id: <20220124184101.335159944@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184100.867127425@linuxfoundation.org> References: <20220124184100.867127425@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Krzysztof Kozlowski commit dded08927ca3c31a5c37f8e7f95fe98770475dd4 upstream. Syzbot detected a NULL pointer dereference of nfc_llcp_sock->dev pointer (which is a 'struct nfc_dev *') with calls to llcp_sock_sendmsg() after a failed llcp_sock_bind(). The message being sent is a SOCK_DGRAM. KASAN report: BUG: KASAN: null-ptr-deref in nfc_alloc_send_skb+0x2d/0xc0 Read of size 4 at addr 00000000000005c8 by task llcp_sock_nfc_a/899 CPU: 5 PID: 899 Comm: llcp_sock_nfc_a Not tainted 5.16.0-rc6-next-20211224-00001-gc6437fbf18b0 #125 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 Call Trace: dump_stack_lvl+0x45/0x59 ? nfc_alloc_send_skb+0x2d/0xc0 __kasan_report.cold+0x117/0x11c ? mark_lock+0x480/0x4f0 ? nfc_alloc_send_skb+0x2d/0xc0 kasan_report+0x38/0x50 nfc_alloc_send_skb+0x2d/0xc0 nfc_llcp_send_ui_frame+0x18c/0x2a0 ? nfc_llcp_send_i_frame+0x230/0x230 ? __local_bh_enable_ip+0x86/0xe0 ? llcp_sock_connect+0x470/0x470 ? llcp_sock_connect+0x470/0x470 sock_sendmsg+0x8e/0xa0 ____sys_sendmsg+0x253/0x3f0 ... The issue was visible only with multiple simultaneous calls to bind() and sendmsg(), which resulted in most of the bind() calls to fail. The bind() was failing on checking if there is available WKS/SDP/SAP (respective bit in 'struct nfc_llcp_local' fields). When there was no available WKS/SDP/SAP, the bind returned error but the sendmsg() to such socket was able to trigger mentioned NULL pointer dereference of nfc_llcp_sock->dev. The code looks simply racy and currently it protects several paths against race with checks for (!nfc_llcp_sock->local) which is NULL-ified in error paths of bind(). The llcp_sock_sendmsg() did not have such check but called function nfc_llcp_send_ui_frame() had, although not protected with lock_sock(). Therefore the race could look like (same socket is used all the time): CPU0 CPU1 ==== ==== llcp_sock_bind() - lock_sock() - success - release_sock() - return 0 llcp_sock_sendmsg() - lock_sock() - release_sock() llcp_sock_bind(), same socket - lock_sock() - error - nfc_llcp_send_ui_frame() - if (!llcp_sock->local) - llcp_sock->local = NULL - nfc_put_device(dev) - dereference llcp_sock->dev - release_sock() - return -ERRNO The nfc_llcp_send_ui_frame() checked llcp_sock->local outside of the lock, which is racy and ineffective check. Instead, its caller llcp_sock_sendmsg(), should perform the check inside lock_sock(). Reported-and-tested-by: syzbot+7f23bcddf626e0593a39@syzkaller.appspotmail.com Fixes: b874dec21d1c ("NFC: Implement LLCP connection less Tx path") Cc: Signed-off-by: Krzysztof Kozlowski Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/nfc/llcp_sock.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/net/nfc/llcp_sock.c +++ b/net/nfc/llcp_sock.c @@ -789,6 +789,11 @@ static int llcp_sock_sendmsg(struct sock lock_sock(sk); + if (!llcp_sock->local) { + release_sock(sk); + return -ENODEV; + } + if (sk->sk_type == SOCK_DGRAM) { DECLARE_SOCKADDR(struct sockaddr_nfc_llcp *, addr, msg->msg_name);