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    Subject[PATCH 4.16 26/81] strparser: Fix incorrect strp->need_bytes value.
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: Doron Roberts-Kedes <doronrk@fb.com>


    [ Upstream commit 9d0c75bf6e03d9bf80c55b0f677dc9b982958fd5 ]

    strp_data_ready resets strp->need_bytes to 0 if strp_peek_len indicates
    that the remainder of the message has been received. However,
    do_strp_work does not reset strp->need_bytes to 0. If do_strp_work
    completes a partial message, the value of strp->need_bytes will continue
    to reflect the needed bytes of the previous message, causing
    future invocations of strp_data_ready to return early if
    strp->need_bytes is less than strp_peek_len. Resetting strp->need_bytes
    to 0 in __strp_recv on handing a full message to the upper layer solves
    this problem.

    __strp_recv also calculates strp->need_bytes using stm->accum_len before
    stm->accum_len has been incremented by cand_len. This can cause
    strp->need_bytes to be equal to the full length of the message instead
    of the full length minus the accumulated length. This, in turn, causes
    strp_data_ready to return early, even when there is sufficient data to
    complete the partial message. Incrementing stm->accum_len before using
    it to calculate strp->need_bytes solves this problem.

    Found while testing net/tls_sw recv path.

    Fixes: 43a0c6751a322847 ("strparser: Stream parser for messages")
    Signed-off-by: Doron Roberts-Kedes <doronrk@fb.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/strparser/strparser.c | 7 +++----
    1 file changed, 3 insertions(+), 4 deletions(-)

    --- a/net/strparser/strparser.c
    +++ b/net/strparser/strparser.c
    @@ -296,9 +296,9 @@ static int __strp_recv(read_descriptor_t
    strp_start_timer(strp, timeo);
    }

    + stm->accum_len += cand_len;
    strp->need_bytes = stm->strp.full_len -
    stm->accum_len;
    - stm->accum_len += cand_len;
    stm->early_eaten = cand_len;
    STRP_STATS_ADD(strp->stats.bytes, cand_len);
    desc->count = 0; /* Stop reading socket */
    @@ -321,6 +321,7 @@ static int __strp_recv(read_descriptor_t
    /* Hurray, we have a new message! */
    cancel_delayed_work(&strp->msg_timer_work);
    strp->skb_head = NULL;
    + strp->need_bytes = 0;
    STRP_STATS_INCR(strp->stats.msgs);

    /* Give skb to upper layer */
    @@ -410,9 +411,7 @@ void strp_data_ready(struct strparser *s
    return;

    if (strp->need_bytes) {
    - if (strp_peek_len(strp) >= strp->need_bytes)
    - strp->need_bytes = 0;
    - else
    + if (strp_peek_len(strp) < strp->need_bytes)
    return;
    }


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