linux-kernel - Re: [PATCH] staging: lusten: conrpc.c: fix different address space sparse warning

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Message-ID: <20170323190901.GA22066@builder>
Date:   Thu, 23 Mar 2017 16:09:03 -0300
From:   Marcos Paulo de Souza <marcos.souza.org@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     devel@...verdev.osuosl.org,
        Doug Oucharek <doug.s.oucharek@...el.com>,
        linux-kernel@...r.kernel.org, Oleg Drokin <oleg.drokin@...el.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andreas Dilger <andreas.dilger@...el.com>,
        lustre-devel@...ts.lustre.org
Subject: Re: [PATCH] staging: lusten: conrpc.c: fix different address space
 sparse warning

On Wed, Mar 29, 2017 at 09:31:14AM +0200, Greg KH wrote:
> On Tue, Mar 28, 2017 at 11:14:06PM -0300, Marcos Paulo de Souza wrote:
> > head_up parameter is marked with __user attribute, tmp is filled
> > by a copy_from_user from next, that is also marked as __user, so
> > tmp.next needs to be "casted" as __user to make sparse happy.
> 
> But is it the correct change?

I don't know, it's my first sparse patch, so I tried to fix this
warning.

> 
> You also have a typo in your subject :(

Sorry, didn't noticed yesterday :(

> 
> > Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@...il.com>
> > ---
> > 
> >  this is mt first patch addressing an issue of sparse, so let me know
> >  if I misunderstood the error message
> > 
> >  drivers/staging/lustre/lnet/selftest/conrpc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/lustre/lnet/selftest/conrpc.c b/drivers/staging/lustre/lnet/selftest/conrpc.c
> > index c6a683b..fb7ad74 100644
> > --- a/drivers/staging/lustre/lnet/selftest/conrpc.c
> > +++ b/drivers/staging/lustre/lnet/selftest/conrpc.c
> > @@ -487,7 +487,7 @@ lstcon_rpc_trans_interpreter(struct lstcon_rpc_trans *trans,
> >  				   sizeof(struct list_head)))
> >  			return -EFAULT;
> >  
> > -		if (tmp.next == head_up)
> > +		if ((struct list_head __user *)tmp.next == head_up)
> 
> Aer you sure this is correct?  __user changes for lustre is not
> trivial...
> 
> How did you test this?

I didn't tested, it just removed the warning. Is this a false positive?

> 
> thanks,
> 
> greg k-h

-- 
Thanks,
	Marcos