From mboxrd@z Thu Jan 1 00:00:00 1970 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 0053DC433EF for ; Mon, 24 Jan 2022 18:48:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245266AbiAXSsY (ORCPT ); Mon, 24 Jan 2022 13:48:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235540AbiAXSsX (ORCPT ); Mon, 24 Jan 2022 13:48:23 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5A359C06173B; Mon, 24 Jan 2022 10:48:23 -0800 (PST) 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 7CA8FB8121A; Mon, 24 Jan 2022 18:48:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B197C340E5; Mon, 24 Jan 2022 18:48:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643050100; bh=n0JbKfVUq1IzLFlzhSKwNzRT5+5ToC4oVt76U2YoAJQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rTaT6vYslAMR/8tMzVe4NP6u8588Px2DwAaJzL7AbrK2rcpScSGVD47HGDClcRVPA oDJK6ws6IzhB28kKsWnzAZm7a4ulEwLpY8Mdu5aOJLQYVxDGYG4rzOaprUynAqYhx4 PsvFlVKDILIJ3FI8ldvLdyYMdcGS8d3qWDv2vkrM= 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 4.4 011/114] nfc: llcp: fix NULL error pointer dereference on sendmsg() after failed bind() Date: Mon, 24 Jan 2022 19:41:46 +0100 Message-Id: <20220124183927.460711078@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124183927.095545464@linuxfoundation.org> References: <20220124183927.095545464@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: 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 @@ -790,6 +790,11 @@ 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);