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    Subject[PATCH 4.18 064/197] tcp, ulp: fix leftover icsk_ulp_ops preventing sock from reattach
    Date
    4.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Daniel Borkmann <daniel@iogearbox.net>

    [ Upstream commit 90545cdc3f2b2ea700e24335610cd181e73756da ]

    I found that in BPF sockmap programs once we either delete a socket
    from the map or we updated a map slot and the old socket was purged
    from the map that these socket can never get reattached into a map
    even though their related psock has been dropped entirely at that
    point.

    Reason is that tcp_cleanup_ulp() leaves the old icsk->icsk_ulp_ops
    intact, so that on the next tcp_set_ulp_id() the kernel returns an
    -EEXIST thinking there is still some active ULP attached.

    BPF sockmap is the only one that has this issue as the other user,
    kTLS, only calls tcp_cleanup_ulp() from tcp_v4_destroy_sock() whereas
    sockmap semantics allow dropping the socket from the map with all
    related psock state being cleaned up.

    Fixes: 1aa12bdf1bfb ("bpf: sockmap, add sock close() hook to remove socks")
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Acked-by: John Fastabend <john.fastabend@gmail.com>
    Acked-by: Song Liu <songliubraving@fb.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/tcp_ulp.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/net/ipv4/tcp_ulp.c
    +++ b/net/ipv4/tcp_ulp.c
    @@ -129,6 +129,8 @@ void tcp_cleanup_ulp(struct sock *sk)
    if (icsk->icsk_ulp_ops->release)
    icsk->icsk_ulp_ops->release(sk);
    module_put(icsk->icsk_ulp_ops->owner);
    +
    + icsk->icsk_ulp_ops = NULL;
    }

    /* Change upper layer protocol for socket */

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