Messages in this thread | | | From | Dmitry Safonov <> | Date | Tue, 6 Feb 2018 01:25:25 +0000 | Subject | Re: [RFC] apparent bogosity in unregister_ftrace_function_probe_func() |
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2018-02-05 22:54 GMT+00:00 Steven Rostedt <rostedt@goodmis.org>: > On Mon, 29 Jan 2018 22:59:42 +0900 > Masami Hiramatsu <mhiramat@kernel.org> wrote: > >> On Sat, 27 Jan 2018 17:07:48 +0000 >> Al Viro <viro@ZenIV.linux.org.uk> wrote: >> >> > 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. >> >> Looks nice to me! >> > > I'll implement this code giving Al credit and referencing this email > thread. Anyone have objections to that?
Thank you, Steven. No objections from me.
-- Dmitry
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