netdev - Re: [PATCH net] strparser: Fix sign of err codes

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Date:   Mon, 26 Mar 2018 13:44:44 -0700
From:   Tom Herbert <tom@...ntonium.net>
To:     Dave Watson <davejwatson@...com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net] strparser: Fix sign of err codes

On Mon, Mar 26, 2018 at 12:31 PM, Dave Watson <davejwatson@...com> wrote:
> strp_parser_err is called with a negative code everywhere, which then
> calls abort_parser with a negative code.  strp_msg_timeout calls
> abort_parser directly with a positive code.  Negate ETIMEDOUT
> to match signed-ness of other calls.
>
> The default abort_parser callback, strp_abort_strp, sets
> sk->sk_err to err.  Also negate the error here so sk_err always
> holds a positive value, as the rest of the net code expects.  Currently
> a negative sk_err can result in endless loops, or user code that
> thinks it actually sent/received err bytes.
>
> Found while testing net/tls_sw recv path.
>
Nice catch!

It might be nice to have a comment at strp_parser_err and abort_parser
description in Documentation/networking/strparser.txt should also be
updated that err is a negative error value.

Tom


> Fixes: 43a0c6751a322847 ("strparser: Stream parser for messages")
> Signed-off-by: Dave Watson <davejwatson@...com>
> ---
>  net/strparser/strparser.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/strparser/strparser.c b/net/strparser/strparser.c
> index 1fdab5c..b9283ce 100644
> --- a/net/strparser/strparser.c
> +++ b/net/strparser/strparser.c
> @@ -60,7 +60,7 @@ static void strp_abort_strp(struct strparser *strp, int err)
>                 struct sock *sk = strp->sk;
>
>                 /* Report an error on the lower socket */
> -               sk->sk_err = err;
> +               sk->sk_err = -err;
>                 sk->sk_error_report(sk);
>         }
>  }
> @@ -458,7 +458,7 @@ static void strp_msg_timeout(struct work_struct *w)
>         /* Message assembly timed out */
>         STRP_STATS_INCR(strp->stats.msg_timeouts);
>         strp->cb.lock(strp);
> -       strp->cb.abort_parser(strp, ETIMEDOUT);
> +       strp->cb.abort_parser(strp, -ETIMEDOUT);
>         strp->cb.unlock(strp);
>  }
>
> --
> 2.9.5
>