tracing: Fix parsing of globs with a wildcard at the beginning

Al Viro reported:

    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.

Testing this with the following:

 # cd /sys/kernel/tracing
 # echo '*raw*lock' > set_ftrace_filter
 bash: echo: write error: Invalid argument

With this patch:

 # echo '*raw*lock' > set_ftrace_filter
 # cat set_ftrace_filter
_raw_read_trylock
_raw_write_trylock
_raw_read_unlock
_raw_spin_unlock
_raw_write_unlock
_raw_spin_trylock
_raw_spin_lock
_raw_write_lock
_raw_read_lock

Al recommended not setting the search buffer to skip the first '*' unless we
know we are not using MATCH_GLOB. This implements his suggested logic.

Link: http://lkml.kernel.org/r/20180127170748.GF13338@ZenIV.linux.org.uk
Cc: stable@vger.kernel.org
Fixes: 60f1d5e3bac44 ("ftrace: Support full glob matching")
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Suggsted-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 61e7f06..a764aec 100644 (file)
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -400,7 +400,6 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
        for (i = 0; i < len; i++) {
                if (buff[i] == '*') {
                        if (!i) {
-                               *search = buff + 1;
                                type = MATCH_END_ONLY;
                        } else if (i == len - 1) {
                                if (type == MATCH_END_ONLY)
@@ -410,14 +409,14 @@ enum regex_type filter_parse_regex(char *buff, int len, char **search, int *not)
                                buff[i] = 0;
                                break;
                        } else {        /* pattern continues, use full glob */
-                               type = MATCH_GLOB;
-                               break;
+                               return MATCH_GLOB;
                        }
                } else if (strchr("[?\\", buff[i])) {
-                       type = MATCH_GLOB;
-                       break;
+                       return MATCH_GLOB;
                }
        }
+       if (buff[0] == '*')
+               *search = buff + 1;
 
        return type;
 }