RE: [PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a function

[Naveen N. Rao]

Excerpts from David Laight's message of April 18, 2017 18:22:
> From: Naveen N. Rao
> > Sent: 12 April 2017 11:58
> ...
> > +kprobe_opcode_t *kprobe_lookup_name(const char *name)
> > +{
> ...
> > +	char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
> > +	const char *modsym;
> > +	bool dot_appended = false;
> > +	if ((modsym = strchr(name, ':')) != NULL) {
> > +		modsym++;
> > +		if (*modsym != '\0' && *modsym != '.') {
> > +			/* Convert to <module:.symbol> */
> > +			strncpy(dot_name, name, modsym - name);
> > +			dot_name[modsym - name] = '.';
> > +			dot_name[modsym - name + 1] = '\0';
> > +			strncat(dot_name, modsym,
> > +				sizeof(dot_name) - (modsym - name) - 2);
> > +			dot_appended = true;
>
> If the ':' is 'a way down' name[] then although the strncpy() won't
> overrun dot_name[] the rest of the code can.

Nice catch, thanks David!
We need to be validating the length of 'name'. I'll put out a patch for 
that.

As an aside, I'm not sure I follow what you mean when you say that the 
strncpy() won't overrun dot_name[]. If we have a name[] longer than 
sizeof(dot_name) with the ':' after that, the strncpy() can also overrun 
dot_name[].


- Naveen

> The strncat() call is particularly borked.
>
> 	David