From nobody Mon Dec 29 00:38:42 2025 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 DED2CC4167B for ; Mon, 4 Dec 2023 13:09:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344277AbjLDNJZ (ORCPT ); Mon, 4 Dec 2023 08:09:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44486 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235478AbjLDNJE (ORCPT ); Mon, 4 Dec 2023 08:09:04 -0500 Received: from sender-of-o51.zoho.in (sender-of-o51.zoho.in [103.117.158.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5739ED5B; Mon, 4 Dec 2023 05:09:05 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701695309; cv=none; d=zohomail.in; s=zohoarc; b=FuJc7I9gI1RkTq8sK+QC5tIAlRPr+gnyONRuBkcwoeFW0R7cEa877xmmErxmSNNcnlm9KZv6ZK/jgdWNvh9HWlLkZAhxlsg8uQ61KhzgH6cwiEQ/vortwlpHmCNwDzaaTUy7IVXqY2lUBjILkUW+JHJz38leeK83bl7zcW41mrU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.in; s=zohoarc; t=1701695309; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=R3iDLTqqyWsCW/yZ9x9fWDYA3oYZ6WCh4COkmNHdQK4=; b=a48H7NBxEMBntfGwtB5CvG3I8k9j5o6RLZ2GJ63nHW0Sl5zTHsWluBLBvNFvai5zsq4ch3DyBgjmlI96msXUujX731N7Eq+M7vKXFPDd4P4YwQnN5D14Cnj+WHDVc8VQRSxDgdD1aw4gx9qjsLs8ugNPQn4mDYscrdlfuPpYmls= ARC-Authentication-Results: i=1; mx.zohomail.in; dkim=pass header.i=siddh.me; spf=pass smtp.mailfrom=code@siddh.me; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1701695309; s=zmail; d=siddh.me; i=code@siddh.me; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Message-Id:Reply-To; bh=R3iDLTqqyWsCW/yZ9x9fWDYA3oYZ6WCh4COkmNHdQK4=; b=CXRmlxmNsWzehyzUEEgqV5rDvEO2SimcT6ofZlkfeHZ4ohHwYY30iC7Z4x0Ggor3 biFmmQqk04h7kN+fDNs+8x6U3xt2q7E9hx1xQflOmRFsi3BbGpPztZoAPhUx2zzPwEQ RFWLQUnYWBp2vWRYwo8gIBieetIzZ8aEwJ1XMlNw= Received: from kampyooter.. (223.229.148.242 [223.229.148.242]) by mx.zoho.in with SMTPS id 1701695308534654.1773373137597; Mon, 4 Dec 2023 18:38:28 +0530 (IST) From: Siddh Raman Pant To: Krzysztof Kozlowski , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Suman Ghosh Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+bbe84a4010eeea00982d@syzkaller.appspotmail.com Subject: [PATCH net-next v3 1/2] nfc: llcp_core: Hold a ref to llcp_local->dev when holding a ref to llcp_local Date: Mon, 4 Dec 2023 18:38:21 +0530 Message-ID: <4143dc4398aa4940a76d3f375ec7984e98891a11.1701627492.git.code@siddh.me> X-Mailer: git-send-email 2.42.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" llcp_sock_sendmsg() calls nfc_llcp_send_ui_frame() which in turn calls nfc_alloc_send_skb(), which accesses the nfc_dev from the llcp_sock for getting the headroom and tailroom needed for skb allocation. Parallelly the nfc_dev can be freed, as the refcount is decreased via nfc_free_device(), leading to a UAF reported by Syzkaller, which can be summarized as follows: (1) llcp_sock_sendmsg() -> nfc_llcp_send_ui_frame() -> nfc_alloc_send_skb() -> Dereference *nfc_dev (2) virtual_ncidev_close() -> nci_free_device() -> nfc_free_device() -> put_device() -> nfc_release() -> Free *nfc_dev When a reference to llcp_local is acquired, we do not acquire the same for the nfc_dev. This leads to freeing even when the llcp_local is in use, and this is the case with the UAF described above too. Thus, when we acquire a reference to llcp_local, we should acquire a reference to nfc_dev, and release the references appropriately later. References for llcp_local is initialized in nfc_llcp_register_device() (which is called by nfc_register_device()). Thus, we should acquire a reference to nfc_dev there. nfc_unregister_device() calls nfc_llcp_unregister_device() which in turn calls nfc_llcp_local_put(). Thus, the reference to nfc_dev is appropriately released later. Reported-and-tested-by: syzbot+bbe84a4010eeea00982d@syzkaller.appspotmail.c= om Closes: https://syzkaller.appspot.com/bug?extid=3Dbbe84a4010eeea00982d Fixes: c7aa12252f51 ("NFC: Take a reference on the LLCP local pointer when = creating a socket") Signed-off-by: Siddh Raman Pant Reviewed-by: Suman Ghosh --- net/nfc/llcp_core.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c index 1dac28136e6a..9d45ce6dcdca 100644 --- a/net/nfc/llcp_core.c +++ b/net/nfc/llcp_core.c @@ -145,6 +145,9 @@ static void nfc_llcp_socket_release(struct nfc_llcp_loc= al *local, bool device, =20 static struct nfc_llcp_local *nfc_llcp_local_get(struct nfc_llcp_local *lo= cal) { + if (!nfc_get_device(local->dev->idx)) + return NULL; + kref_get(&local->ref); =20 return local; @@ -180,6 +183,7 @@ int nfc_llcp_local_put(struct nfc_llcp_local *local) if (local =3D=3D NULL) return 0; =20 + nfc_put_device(local->dev); return kref_put(&local->ref, local_release); } =20 @@ -959,8 +963,18 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_loca= l *local, } =20 new_sock =3D nfc_llcp_sock(new_sk); - new_sock->dev =3D local->dev; + new_sock->local =3D nfc_llcp_local_get(local); + if (!new_sock->local) { + reason =3D LLCP_DM_REJ; + release_sock(&sock->sk); + sock_put(&sock->sk); + sock_put(&new_sock->sk); + nfc_llcp_sock_free(new_sock); + goto fail; + } + + new_sock->dev =3D local->dev; new_sock->rw =3D sock->rw; new_sock->miux =3D sock->miux; new_sock->nfc_protocol =3D sock->nfc_protocol; @@ -1597,7 +1611,13 @@ int nfc_llcp_register_device(struct nfc_dev *ndev) if (local =3D=3D NULL) return -ENOMEM; =20 - local->dev =3D ndev; + /* Hold a reference to the device. */ + local->dev =3D nfc_get_device(ndev->idx); + if (!local->dev) { + kfree(local); + return -ENODEV; + } + INIT_LIST_HEAD(&local->list); kref_init(&local->ref); mutex_init(&local->sdp_lock); --=20 2.42.0