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

[Marcos Paulo de Souza]

On Wed, Mar 29, 2017 at 12:34:05PM +0200, Greg KH wrote:
> On Thu, Mar 23, 2017 at 04:09:03PM -0300, Marcos Paulo de Souza wrote:
> > 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@xxxxxxxxx>
> > > > ---
> > > > 
> > > >  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?
> 
> I don't know, it's up to you to prove to me that you know this change is
> correct.  You have to justify your changes, and "because checkpatch.pl
> complained" isn't a valid justification for something like this :)

Fair enough, I'll take in another sparse report to work on. Thanks!

> 
> thanks,
> 
> greg k-h

-- 
Thanks,
	Marcos