On 2021/3/3 17:28, kiyin(尹亮) wrote:
Hi xiaoming, the path can only fix the endless loop problem. it can't fix the meaningless llcp_sock->service_name problem. if we set llcp_sock->service_name to meaningless string, the connect will be failed. and sk->sk_state will not be LLCP_CONNECTED. then we can call llcp_sock_connect() many times. that leaks everything: llcp_sock->dev, llcp_sock->local, llcp_sock->ssap, llcp_sock->service_name...
I didn't find the code to modify sk->sk_state after a connect failure. Can you provide guidance?
Based on my understanding of the current code: After llcp_sock_connect() is invoked using the meaningless service_name as the parameter, sk->sk_state is set to LLCP_CONNECTING. After that, no corresponding service responds to the request because the service_name is meaningless, the value of sk->sk_state remains unchanged. Therefore, when llcp_sock_connect() is invoked again, resources such as llcp_sock->service_name are not repeatedly applied because sk_state is set to LLCP_CONNECTING.
In this way, the repeated invoking of llcp_sock_connect() does not repeatedly leak resources.
Thanks Xiaoming Ni
-----Original Message----- From: Xiaoming Ni [mailto:nixiaoming@huawei.com] Sent: Wednesday, March 3, 2021 2:17 PM To: linux-kernel@vger.kernel.org; kiyin(尹亮) kiyin@tencent.com; stable@vger.kernel.org; gregkh@linuxfoundation.org; sameo@linux.intel.com; linville@tuxdriver.com; davem@davemloft.net; kuba@kernel.org; mkl@pengutronix.de; stefan@datenfreihafen.org; matthieu.baerts@tessares.net; netdev@vger.kernel.org Cc: nixiaoming@huawei.com; wangle6@huawei.com; xiaoqian9@huawei.com Subject: [PATCH 4/4] nfc: Avoid endless loops caused by repeated llcp_sock_connect()(Internet mail)
When sock_wait_state() returns -EINPROGRESS, "sk->sk_state" is LLCP_CONNECTING. In this case, llcp_sock_connect() is repeatedly invoked, nfc_llcp_sock_link() will add sk to local->connecting_sockets twice. sk->sk_node->next will point to itself, that will make an endless loop and hang-up the system. To fix it, check whether sk->sk_state is LLCP_CONNECTING in llcp_sock_connect() to avoid repeated invoking.
fix CVE-2020-25673 Fixes: b4011239a08e ("NFC: llcp: Fix non blocking sockets connections") Reported-by: "kiyin(尹亮)" kiyin@tencent.com Link: https://www.openwall.com/lists/oss-security/2020/11/01/1 Cc: stable@vger.kernel.org #v3.11 Signed-off-by: Xiaoming Ni nixiaoming@huawei.com
net/nfc/llcp_sock.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c index 59172614b249..a3b46f888803 100644 --- a/net/nfc/llcp_sock.c +++ b/net/nfc/llcp_sock.c @@ -673,6 +673,10 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr, ret = -EISCONN; goto error; }
if (sk->sk_state == LLCP_CONNECTING) {
ret = -EINPROGRESS;goto error;}
dev = nfc_get_device(addr->dev_idx); if (dev == NULL) {
-- 2.27.0