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    Subject[PATCH 5.13 525/800] mptcp: fix 32 bit DSN expansion
    Date
    From: Paolo Abeni <pabeni@redhat.com>

    [ Upstream commit 5957a8901db44c03540505ccedd95031c21ef2f2 ]

    The current implementation of 32 bit DSN expansion is buggy.
    After the previous patch, we can simply reuse the newly
    introduced helper to do the expansion safely.

    Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/120
    Fixes: 648ef4b88673 ("mptcp: Implement MPTCP receive path")
    Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/mptcp/subflow.c | 17 +----------------
    1 file changed, 1 insertion(+), 16 deletions(-)

    diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
    index 3a396451d628..f5bb3a0e9975 100644
    --- a/net/mptcp/subflow.c
    +++ b/net/mptcp/subflow.c
    @@ -775,15 +775,6 @@ enum mapping_status {
    MAPPING_DUMMY
    };

    -static u64 expand_seq(u64 old_seq, u16 old_data_len, u64 seq)
    -{
    - if ((u32)seq == (u32)old_seq)
    - return old_seq;
    -
    - /* Assume map covers data not mapped yet. */
    - return seq | ((old_seq + old_data_len + 1) & GENMASK_ULL(63, 32));
    -}
    -
    static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
    {
    pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
    @@ -907,13 +898,7 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
    data_len--;
    }

    - if (!mpext->dsn64) {
    - map_seq = expand_seq(subflow->map_seq, subflow->map_data_len,
    - mpext->data_seq);
    - pr_debug("expanded seq=%llu", subflow->map_seq);
    - } else {
    - map_seq = mpext->data_seq;
    - }
    + map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
    WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);

    if (subflow->map_valid) {
    --
    2.30.2


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