Re: [PATCH v4 3/7] kprobes: validate the symbol name provided during probe registration

[Naveen N. Rao]

Excerpts from Paul Clarke's message of April 21, 2017 18:41:
> a nit or two, below...
>
> On 04/21/2017 07:32 AM, Naveen N. Rao wrote:
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 6a128f3a7ed1..ff9b1ac72a38 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -1383,6 +1383,34 @@ bool within_kprobe_blacklist(unsigned long addr)
> >  }
> >
> >  /*
> > + * We mainly want to ensure that the provided string is of a reasonable length
> > + * and is of the form [<mod_name>:]<sym_name>, so that this is safe to process
> > + * further.
> > + * We don't worry about invalid characters as those will just prevent
> > + * matching existing kallsyms.
> > + */
> > +bool is_valid_kprobe_symbol_name(const char *name)
> > +{
> > +	size_t sym_len;
> > +	const char *s;
> > +
> > +	s = strnchr(name, ':', MODULE_NAME_LEN + KSYM_NAME_LEN + 1);
> > +	if (s) {
> > +		sym_len = (size_t)(s - name);
> > +		if (sym_len <= 0  || sym_len >= MODULE_NAME_LEN)
>
> "sym_len <= 0" looks odd here, since sym_len is likely unsigned and would never be less than zero, anyway.

Ugh.. habits :/
I'll wait for Masami/Michael's feedback before re-spinning.

Thanks for the review,
- Naveen