linux-kernel - Re: [PATCH 5/5] logger: clarify non-update of w_off in do_write_log_from

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Message-ID: <CAPz4a6CrJ2VS8-igOz5aRFAL32-xUi5a6cHa6rEqtK3B5689Og@mail.gmail.com>
Date:	Wed, 8 Feb 2012 22:10:54 -0800
From:	Dima Zavin <dima@...roid.com>
To:	Tim Bird <tim.bird@...sony.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	linux-embedded <linux-embedded@...r.kernel.org>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH 5/5] logger: clarify non-update of w_off in do_write_log_from_user

On Tue, Feb 7, 2012 at 6:34 PM, Tim Bird <tim.bird@...sony.com> wrote:
> Add comment to explain when w_off is not updated in case of failed second
> fragment copy to buffer.
>
> Signed-off-by: Tim Bird <tim.bird@...sony.com>

Acked-by: Dima Zavin <dima@...roid.com>

> ---
>  drivers/staging/android/logger.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c
> index 8d9d4f1..115d8ed 100644
> --- a/drivers/staging/android/logger.c
> +++ b/drivers/staging/android/logger.c
> @@ -330,6 +330,12 @@ static ssize_t do_write_log_from_user(struct logger_log *log,
>
>        if (count != len)
>                if (copy_from_user(log->buffer, buf + len, count - len))
> +                       /*
> +                        * Note that by not updating w_off, this abandons the
> +                        * portion of the new entry that *was* successfully
> +                        * copied, just above.  This is intentional to avoid
> +                        * message corruption from missing fragments.
> +                        */
>                        return -EFAULT;
>
>        log->w_off = logger_offset(log, log->w_off + count);
> --
> 1.7.2.3
>
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