On Sat, Jan 27, 2018 at 01:59:56PM +0000, Dmitry Safonov wrote:
>
> > Incidentally, shouldn't filter_parse_regex("*[ab]", 5, &s, ¬)
> > end up with s = "*[ab]"? We are returning MATCH_GLOB, after all,
> > so we want the entire pattern there... I would've assumed that
> > this is what the code in unregister_ftrace_function_probe_func()
> > is trying to compensate for, the first oddity predates MATCH_GLOB...
>
> No, I don't think filter_parse_regex() should return the full regex..
> ftrace_match() expects search would be processed string, not a glob.
> So, this unnecessary assignment broke unregistering multiple kprobs
> with a middle/end pattern..
For substring - sure, but what about something like "*a*b" and "a*b"?
AFAICS, filter_parse_regex() ends up with identical results in both
cases - MATCH_GLOB and *search = "a*b". And no way for the caller
to tell one from another.
IOW, it's a different bug sometimes obscured by the one in
unregister_ftrace_function_probe_func(). filter_parse_regex()
ought to revert to *search = buff; when it decides to return
MATCH_GLOB. Or something like
for (i = 0; i < len; i++) {
if (buff[i] == '*') {
if (!i) {
type = MATCH_END_ONLY;
} else if (i == len - 1) {
if (type == MATCH_END_ONLY)
type = MATCH_MIDDLE_ONLY;
else
type = MATCH_FRONT_ONLY;
buff[i] = 0;
break;
} else { /* pattern continues, use full glob */
return MATCH_GLOB;
}
} else if (strchr("[?\\", buff[i])) {
return MATCH_GLOB;
}
}
if (buff[0] == '*')
*search = buff + 1;
for that matter - i.e. delay that "we want everything past the first character"
until we are certain it's not a MATCH_GLOB.
That one was introduced by "ftrace: Support full glob matching" in 2016,
AFAICS...
