Re: [PATCH] lseek: ensure errno is set on failure and return -1

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Feb 23, 2017 at 10:28:41PM +0100, Uwe Kleine-König wrote:
> All error paths before calling the driver's lseek callback return -1 and
> set errno. Do the same if the callback returns an error.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>  fs/fs.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/fs.c b/fs/fs.c
> index 2b4659cfbb76..e7b696591433 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -926,7 +926,13 @@ loff_t lseek(int fildes, loff_t offset, int whence)
>  		goto out;
>  	}
>  
> -	return fsdrv->lseek(&f->fsdev->dev, f, pos);
> +	pos = fsdrv->lseek(&f->fsdev->dev, f, pos);
> +	if (pos < 0) {
> +		errno = -pos;
> +		return -1;
> +	}

Before calling into the drivers lseek checks if the position is within
the bounds of the file. So when fsdrv->lseek() returns successfully then
the position must be the same that was passed in. I think we can just
let fsdrv->lseek() return an error code rather than the file position.

Sascha

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