From patchwork Tue Dec 12 18:49:19 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Siddh Raman Pant X-Patchwork-Id: 13489778 X-Patchwork-Delegate: kuba@kernel.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=siddh.me header.i=code@siddh.me header.b="t4B/dsuU" Received: from sender-of-o51.zoho.in (sender-of-o51.zoho.in [103.117.158.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FB19CE; Tue, 12 Dec 2023 10:50:03 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1702406966; cv=none; d=zohomail.in; s=zohoarc; b=LGV/XknIHZ+zp7YLAnIG2Oe/Fr8L0fSEC3pG4DIXSGqwNAYldOXKILF/9NL165pS1gHapoF2XmTqc9NcVsfM/8GeEfZLkvJ0M2J2hSi1I4gTbuqYhM6+vjGQIlQxbpmtXPnh0UVthnTN6j8lJGcjiHaaoeFqf0S126P+B+LXf+4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.in; s=zohoarc; t=1702406966; 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=7RCDvTtCKRGsE+W0Q84GxYSqs2sZMkWAKNJDaj4VdG8=; b=adlWOXZUodTgBEJ0zwVHScx6iAztlGzt9k0NHOROdBCyI9xwsrWn2hfyXQQgBiRPvHGOgxKkXkdZC+F/+0JY0c+DN37f7RXiHI+l/X74SBR8cQW7hT61ih+EYRypQ/1ZJ4f6Tf7c41KtxE9QmkYYKVfs+SJ3QiPFoVoje4lH/eE= 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=1702406966; 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=7RCDvTtCKRGsE+W0Q84GxYSqs2sZMkWAKNJDaj4VdG8=; b=t4B/dsuU2ewzZQ07xfGwoz/zZ6XbnDj1khhgUaKOEKfIJVE0n2YLYISlP+0eHSK0 3hdMvYU/SvydF+5IDvKXv1TppmYtwzV33qWA9dMwfN5Va0HAYu17I0cPKD5WVC6sPTI AqAY72RjPV62huIfS98+TefTnFHi/2UpK/9a+gJ8= Received: from kampyooter.. (182.69.31.144 [182.69.31.144]) by mx.zoho.in with SMTPS id 1702406965792752.930614411838; Wed, 13 Dec 2023 00:19:25 +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 v5 1/2] nfc: llcp_core: Hold a ref to llcp_local->dev when holding a ref to llcp_local Date: Wed, 13 Dec 2023 00:19:19 +0530 Message-ID: <6a26e3b65817bb31cb11c8dde5b1b420071d944e.1702404519.git.code@siddh.me> X-Mailer: git-send-email 2.42.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ZohoMailClient: External X-Patchwork-Delegate: kuba@kernel.org 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.com Closes: https://syzkaller.appspot.com/bug?extid=bbe84a4010eeea00982d Fixes: c7aa12252f51 ("NFC: Take a reference on the LLCP local pointer when creating a socket") Reviewed-by: Suman Ghosh Signed-off-by: Siddh Raman Pant --- net/nfc/llcp_core.c | 72 +++++++++++++++++++++++++++++---------------- 1 file changed, 47 insertions(+), 25 deletions(-) diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c index 1dac28136e6a..2f77200a3720 100644 --- a/net/nfc/llcp_core.c +++ b/net/nfc/llcp_core.c @@ -145,6 +145,13 @@ static void nfc_llcp_socket_release(struct nfc_llcp_local *local, bool device, static struct nfc_llcp_local *nfc_llcp_local_get(struct nfc_llcp_local *local) { + /* Since using nfc_llcp_local may result in usage of nfc_dev, whenever + * we hold a reference to local, we also need to hold a reference to + * the device to avoid UAF. + */ + if (!nfc_get_device(local->dev->idx)) + return NULL; + kref_get(&local->ref); return local; @@ -177,10 +184,18 @@ static void local_release(struct kref *ref) int nfc_llcp_local_put(struct nfc_llcp_local *local) { + struct nfc_dev *dev; + int ret; + if (local == NULL) return 0; - return kref_put(&local->ref, local_release); + dev = local->dev; + + ret = kref_put(&local->ref, local_release); + nfc_put_device(dev); + + return ret; } static struct nfc_llcp_sock *nfc_llcp_sock_get(struct nfc_llcp_local *local, @@ -901,7 +916,7 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local, if (dsap != LLCP_SAP_SDP) { sock = nfc_llcp_sock_get(local, dsap, LLCP_SAP_SDP); - if (sock == NULL || sock->sk.sk_state != LLCP_LISTEN) { + if (!sock || sock->sk.sk_state != LLCP_LISTEN) { reason = LLCP_DM_NOBOUND; goto fail; } @@ -910,7 +925,7 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local, size_t sn_len; sn = nfc_llcp_connect_sn(skb, &sn_len); - if (sn == NULL) { + if (!sn) { reason = LLCP_DM_NOBOUND; goto fail; } @@ -918,7 +933,7 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local, pr_debug("Service name length %zu\n", sn_len); sock = nfc_llcp_sock_get_sn(local, sn, sn_len); - if (sock == NULL) { + if (!sock) { reason = LLCP_DM_NOBOUND; goto fail; } @@ -928,39 +943,31 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local, parent = &sock->sk; - if (sk_acceptq_is_full(parent)) { - reason = LLCP_DM_REJ; - release_sock(&sock->sk); - sock_put(&sock->sk); - goto fail; - } + if (sk_acceptq_is_full(parent)) + goto fail_put_sock; if (sock->ssap == LLCP_SDP_UNBOUND) { u8 ssap = nfc_llcp_reserve_sdp_ssap(local); pr_debug("First client, reserving %d\n", ssap); - if (ssap == LLCP_SAP_MAX) { - reason = LLCP_DM_REJ; - release_sock(&sock->sk); - sock_put(&sock->sk); - goto fail; - } + if (ssap == LLCP_SAP_MAX) + goto fail_put_sock; sock->ssap = ssap; } new_sk = nfc_llcp_sock_alloc(NULL, parent->sk_type, GFP_ATOMIC, 0); - if (new_sk == NULL) { - reason = LLCP_DM_REJ; - release_sock(&sock->sk); - sock_put(&sock->sk); - goto fail; - } + if (!new_sk) + goto fail_put_sock; new_sock = nfc_llcp_sock(new_sk); - new_sock->dev = local->dev; + new_sock->local = nfc_llcp_local_get(local); + if (!new_sock->local) + goto fail_free_new_sock; + + new_sock->dev = local->dev; new_sock->rw = sock->rw; new_sock->miux = sock->miux; new_sock->nfc_protocol = sock->nfc_protocol; @@ -1004,8 +1011,14 @@ static void nfc_llcp_recv_connect(struct nfc_llcp_local *local, return; +fail_free_new_sock: + sock_put(&new_sock->sk); + nfc_llcp_sock_free(new_sock); +fail_put_sock: + reason = LLCP_DM_REJ; + release_sock(&sock->sk); + sock_put(&sock->sk); fail: - /* Send DM */ nfc_llcp_send_dm(local, dsap, ssap, reason); } @@ -1597,7 +1610,16 @@ int nfc_llcp_register_device(struct nfc_dev *ndev) if (local == NULL) return -ENOMEM; - local->dev = ndev; + /* As we are going to initialize local's refcount, we need to get the + * nfc_dev to avoid UAF, otherwise there is no point in continuing. + * See nfc_llcp_local_get(). + */ + local->dev = 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);