On Tue, Dec 10, 2019 at 11:19:13AM -0800, Eric Biggers wrote:
> > +static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
> > +{
> > + if (unlikely(name[0] == '.')) {
> > + if (len < 2 || (len == 2 && name[1] == '.'))
> > + return true;
> > + }
> > +
> > + return false;
> > +}
>
> This doesn't handle the len=0 case. Did you check that none of the users pass
> in zero-length names? It looks like fscrypt_fname_disk_to_usr() can, if the
> directory entry on-disk has a zero-length name. Currently it will return
> -EUCLEAN in that case, but with this patch it may think it's the name ".".
>
> So I think there needs to either be a len >= 1 check added, *or* you need to
> make an argument for why it's okay to not care about the empty name case.
Frankly, the only caller that matters in practice is link_path_walk(); _that_
is by far the hottest path that might make use of that thing.
BTW, the callers that might end up passing 0 for len really ought to take
a good look at another thing - that name[0] is, in fact, mapped. Something
along the lines of
if (name + len > end_of_buffer)
sod off
if (<that function>(name, len))
....
is not enough, for obvious reasons.
