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From: "M. Mohan Kumar" <mohan@in.ibm.com>
Subject: Re: [Qemu-devel] [V3 PATCH 7/8] virtio-9p: Move file post creation
	changes to none security model
Date: Thu, 20 Jan 2011 20:11:27 +0530
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: qemu-devel@nongnu.org

On Thursday 20 January 2011 2:29:54 pm Stefan Hajnoczi wrote:
> On Tue, Jan 18, 2011 at 01:54:16PM +0530, M. Mohan Kumar wrote:

> > -    if (lchown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid) < 0)=
 {
> > -        /*
> > -         * If we fail to change ownership and if we are
> > -         * using security model none. Ignore the error
> > -         */
> > -        if (fs_ctx->fs_sm !=3D SM_NONE) {
> > -            return -1;
> > -        }
> > -    }
> > +    retval =3D lchown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gi=
d);
> >=20
> >      return 0;
> > =20
> >  }
>=20
> retval is unused.
>=20

That was used to disable the warning message "error: ignoring return value =
of=20
=E2=80=98lchown=E2=80=99, declared with attribute warn_unused_result"

Otherwise I have to use
if (lchown(rpath(fs_ctx, path), credp->fc_uid, credp->fc_gid)) {
	;
}

> Can multiple virtio-9p requests execute at a time?  chmod() and lchown()
> after creation is a race condition if other requests can execute
> concurrently.
>=20

We can't implement file creation with requested user credentials and permis=
sion=20
bits in the none security model atomically. Its expected behaviour only

=2D---
M. Mohan Kumar