Re: [PATCH net] strparser: Fix incorrect strp->need_bytes value.

[David Miller <davem@davemloft.net>]

From: Doron Roberts-Kedes <doronrk@fb.com>
Date: Wed, 11 Apr 2018 15:05:16 -0700

> 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>

Applied and queued up for -stable.