On Wed, 19 Oct 2022 07:28:45 -0400 Brian Foster <bfoster@xxxxxxxxxx> wrote:
> On Tue, Oct 18, 2022 at 11:51:02AM -0700, Ivan Babrou wrote:
> > On Tue, Oct 18, 2022 at 11:16 AM Brian Foster <bfoster@xxxxxxxxxx> wrote:
> > > > +static int proc_readfd_count(struct inode *inode)
> > > > +{
> > > > + struct task_struct *p = get_proc_task(inode);
> > > > + struct fdtable *fdt;
> > > > + unsigned int open_fds = 0;
> > > > +
> > > > + if (!p)
> > > > + return -ENOENT;
> > >
> > > Maybe this shouldn't happen, but do you mean to assign the error code to
> > > stat->size in the caller? Otherwise this seems reasonable to me.
> >
> > You are right. As unlikely as it is to happen, we shouldn't return
> > negative size.
> >
> > What's the idiomatic way to make this work? My two options are:
> >
> > 1. Pass &stat->size into proc_readfd_count:
> >
> > if (S_ISDIR(inode->i_mode)) {
> > rv = proc_readfd_count(inode, &stat->size);
> > if (rv < 0)
> > goto out;
> > }
> >
> > out:
> > return rv;
> >
> > OR without a goto:
> >
> > if (S_ISDIR(inode->i_mode)) {
> > rv = proc_readfd_count(inode, &stat->size));
> > if (rv < 0)
> > return rv;
> > }
> >
> > return rv;
> >
> > 2. Return negative count as error (as we don't expect negative amount
> > of files open):
> >
> > if (S_ISDIR(inode->i_mode)) {
> > size = proc_readfd_count(inode);
> > if (size < 0)
> > return size;
> > stat->size = size;
> > }
> >
>
> I suppose the latter is less of a change to the original patch..? Either
> way seems reasonable to me. I have no strong preference FWIW.
If get_proc_task() failed then something has gone horridly wrong,
hasn't it? Wouldn't it make sense in this situation to make the
.getattr() itself return an errno, in which case the data at *stat
dosen't matter - it's invalid anyway.
This seems to be the general approach in procfs when get_proc_task()
fails - return -ESRCH (or, seemingly randomly, -ENOENT) to the caller.
