linux-kernel - Re: [PATCH 8/9] fs: nfs: misused copy_to

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Date:	Fri, 30 Jul 2010 22:03:30 +0400
From:	Vasiliy Kulikov <segooon@...il.com>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	kernel-janitors@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/9] fs: nfs: misused copy_to_user() return value

On Fri, Jul 30, 2010 at 13:47 -0400, Trond Myklebust wrote:
> On Fri, 2010-07-30 at 15:09 +0400, Kulikov Vasiliy wrote:
> > copy_to_user() returns nonzero value on error, this value may be any
> > value between 0 and requested count, not only requested count.
> > 
> > Signed-off-by: Kulikov Vasiliy <segooon@...il.com>
> > ---
> >  fs/nfs/idmap.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
> > index 21a84d4..a9f2cd5 100644
> > --- a/fs/nfs/idmap.c
> > +++ b/fs/nfs/idmap.c
> > @@ -362,7 +362,7 @@ idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
> >  	unsigned long left;
> >  
> >  	left = copy_to_user(dst, data, mlen);
> > -	if (left == mlen) {
> > +	if (left)
> >  		msg->errno = -EFAULT;
> >  		return -EFAULT;
> >  	}
> 
> ...and we do handle the case where copy_to_user returns less than the
> requested number of bytes: it is called a 'short read' and is quite
> allowed in POSIX. The userland application can just call sys_read()
> again...

Right, please ignore these 2 patches.

> 
> Trond
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