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SubjectRe: [rfc] fcntl: Add F_GETOWNER_UIDS option
On Mon, Mar 26, 2012 at 06:43:47PM +0200, Oleg Nesterov wrote:
> On 03/26, Cyrill Gorcunov wrote:
> >
> > +#ifdef CONFIG_CHECKPOINT_RESTORE
> > +static int f_getowner_uids(struct file *filp, unsigned long arg)
> > +{
> > + struct user_namespace *user_ns = current_user_ns();
> > + const struct cred *cred = current_cred();
> > + uid_t * __user dst = (void * __user)arg;
> > + uid_t src[2];
> > + int err;
> > +
> > + read_lock(&filp->f_owner.lock);
> > + src[0] = filp->f_owner.uid;
> > + src[1] = filp->f_owner.euid;
> > + read_unlock(&filp->f_owner.lock);
> > +
> > + src[0] = user_ns_map_uid(user_ns, cred, src[0]);
> > + src[1] = user_ns_map_uid(user_ns, cred, src[1]);
>
> Why?
>
> In this case user_ns_map_uid() is "nop", it should always return
> the last arg, no?

Yes, but I wanted to be on safe side, and if one day user_ns_map_uid
get changed this function won't be security hole. Or I miss something
in general?

Cyrill


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