linux-kernel - Re: [PATCH RFC 4/5] kdbus: handle WARN_ON cases properly when decrementing quota

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Date:	Thu, 2 Jul 2015 10:37:05 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	Sergei Zviagintsev <sergei@...v.net>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 4/5] kdbus: handle WARN_ON cases properly when
 decrementing quota

Hi

On Sun, Jun 28, 2015 at 3:17 PM, Sergei Zviagintsev <sergei@...v.net> wrote:
> If we spotted inconsistency, fix it by setting values to zero.

Why?

I prefer doing nothing and just bailing out on programming errors.
Setting it to 0 just complicates debugging and drops possibly useful
information ('what was the counter value at that time?').

Thanks
David

> Signed-off-by: Sergei Zviagintsev <sergei@...v.net>
> ---
>  ipc/kdbus/connection.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/ipc/kdbus/connection.c b/ipc/kdbus/connection.c
> index 1d44e280eff0..12e32de310f5 100644
> --- a/ipc/kdbus/connection.c
> +++ b/ipc/kdbus/connection.c
> @@ -742,9 +742,15 @@ void kdbus_conn_quota_dec(struct kdbus_conn *c, struct kdbus_user *u,
>
>         if (!WARN_ON(quota->msgs == 0))
>                 --quota->msgs;
> -       if (!WARN_ON(quota->memory < memory))
> +
> +       if (WARN_ON(quota->memory < memory))
> +               quota->memory = 0;
> +       else
>                 quota->memory -= memory;
> -       if (!WARN_ON(quota->fds < fds))
> +
> +       if (WARN_ON(quota->fds < fds))
> +               quota->fds = 0;
> +       else
>                 quota->fds -= fds;
>  }
>
> --
> 1.8.3.1
>
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