linux-kernel - Re: [PATCH] fsi: fix bogos error returns from cfam_read and cfam

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Date:   Thu, 28 Nov 2019 23:20:38 +0000
From:   Joel Stanley <joel@....id.au>
To:     Colin King <colin.king@...onical.com>
Cc:     Jeremy Kerr <jk@...abs.org>,
        Alistar Popple <alistair@...ple.id.au>,
        Eddie James <eajames@...ux.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-fsi@...ts.ozlabs.org, kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fsi: fix bogos error returns from cfam_read and cfam_write

Hi Colin,

On Fri, 22 Nov 2019 at 23:31, Colin King <colin.king@...onical.com> wrote:
>
> From: Colin Ian King <colin.king@...onical.com>
>
> In the case where errors occur in functions cfam_read and cfam_write
> the error return code in rc is not returned and a bogus non-error
> count size is returned instead. Fix this by returning the correct
> error code when an error occurs or the count size if the functions
> worked correctly.

 You're correct that if there's an error we need to return an error.

However the other case is when there's a partial read that completed.
We already advance the file offset, but I think we should also return
the number of bytes successfully read.

Cheers,

Joel

>
> Addresses-Coverity: ("Unused value")
> Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/fsi/fsi-core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
> index 8244da8a7241..c3885b138ead 100644
> --- a/drivers/fsi/fsi-core.c
> +++ b/drivers/fsi/fsi-core.c
> @@ -718,7 +718,7 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
>         rc = count;
>   fail:
>         *offset = off;
> -       return count;
> +       return rc;
>  }
>
>  static ssize_t cfam_write(struct file *filep, const char __user *buf,
> @@ -755,7 +755,7 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
>         rc = count;
>   fail:
>         *offset = off;
> -       return count;
> +       return rc;
>  }
>
>  static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)
> --
> 2.24.0
>