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    Subject[PATCH 4.9 31/49] net/vmw_vsock: improve locking in vsock_connect_timeout()
    Date
    From: Norbert Slusarek <nslusarek@gmx.net>

    commit 3d0bc44d39bca615b72637e340317b7899b7f911 upstream.

    A possible locking issue in vsock_connect_timeout() was recognized by
    Eric Dumazet which might cause a null pointer dereference in
    vsock_transport_cancel_pkt(). This patch assures that
    vsock_transport_cancel_pkt() will be called within the lock, so a race
    condition won't occur which could result in vsk->transport to be set to NULL.

    Fixes: 380feae0def7 ("vsock: cancel packets when failing to connect")
    Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: Norbert Slusarek <nslusarek@gmx.net>
    Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
    Link: https://lore.kernel.org/r/trinity-f8e0937a-cf0e-4d80-a76e-d9a958ba3ef1-1612535522360@3c-app-gmx-bap12
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/vmw_vsock/af_vsock.c | 5 +----
    1 file changed, 1 insertion(+), 4 deletions(-)

    --- a/net/vmw_vsock/af_vsock.c
    +++ b/net/vmw_vsock/af_vsock.c
    @@ -1121,7 +1121,6 @@ static void vsock_connect_timeout(struct
    {
    struct sock *sk;
    struct vsock_sock *vsk;
    - int cancel = 0;

    vsk = container_of(work, struct vsock_sock, connect_work.work);
    sk = sk_vsock(vsk);
    @@ -1132,11 +1131,9 @@ static void vsock_connect_timeout(struct
    sk->sk_state = SS_UNCONNECTED;
    sk->sk_err = ETIMEDOUT;
    sk->sk_error_report(sk);
    - cancel = 1;
    + vsock_transport_cancel_pkt(vsk);
    }
    release_sock(sk);
    - if (cancel)
    - vsock_transport_cancel_pkt(vsk);

    sock_put(sk);
    }

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