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    Subject[PATCH 4.14 06/68] nfc: Avoid endless loops caused by repeated llcp_sock_connect()
    Date
    From: Xiaoming Ni <nixiaoming@huawei.com>

    commit 4b5db93e7f2afbdfe3b78e37879a85290187e6f1 upstream.

    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.

    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>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/nfc/llcp_sock.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/net/nfc/llcp_sock.c
    +++ b/net/nfc/llcp_sock.c
    @@ -686,6 +686,10 @@ static int llcp_sock_connect(struct sock
    ret = -EISCONN;
    goto error;
    }
    + if (sk->sk_state == LLCP_CONNECTING) {
    + ret = -EINPROGRESS;
    + goto error;
    + }

    dev = nfc_get_device(addr->dev_idx);
    if (dev == NULL) {

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