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

[Uwe Kleine-König]

Hello Sascha,

On Fri, Feb 24, 2017 at 08:45:13AM +0100, Sascha Hauer wrote:
> 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 at 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.

This is a separate and orthogonal change however that doesn't make my
patch wrong.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |