Re: [Qemu-devel] [Xen-devel] [PATCH v3 07/11] igd: revamp host config read

[Stefano Stabellini]

On Wed, 6 Jan 2016, Gerd Hoffmann wrote:
> > > +    for (i = 0; i < len; i++) {
> > > +        rc = pread(config_fd, guest->config + list[i].offset,
> > > +                   list[i].len, list[i].offset);
> > > +        if (rc != list[i].len) {
> > 
> > pread is allowed to return early, returning the number of bytes read.
> > 
> 
> This is a sysfs file though, not a socket or pipe where a partial read
> makes sense and will actually happen.  If we can't read something
> that'll be because the kernel denies access.
> 
> So IMHO it should be fine to treat anything which doesn't give us the
> amount of bytes we asked for as an error condition.

True, still theoretically, it's possible for pread to return early. Who
knows what glibc and linux are going to do in the future.