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From:   Xiaoming Ni <nixiaoming@huawei.com>
To:     <linux-kernel@vger.kernel.org>, <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()
Date:   Wed, 3 Mar 2021 14:16:54 +0800
Message-ID: <20210303061654.127666-5-nixiaoming@huawei.com>
In-Reply-To: <20210303061654.127666-1-nixiaoming@huawei.com>
References: <20210303061654.127666-1-nixiaoming@huawei.com>
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Precedence: bulk

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