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

Web:        https://git.kernel.org/torvalds/c/07234021410bbc27b7c86c18de98616c29fbe667
Commit:     07234021410bbc27b7c86c18de98616c29fbe667
Parent:     7b6586562708d2b3a04fe49f217ddbadbbbb0546
Refname:    refs/heads/master
Author:     Steven Rostedt (VMware) <[email protected]>
AuthorDate: Mon Feb 5 22:18:11 2018 -0500
Committer:  Steven Rostedt (VMware) <[email protected]>
CommitDate: Thu Feb 8 10:11:47 2018 -0500

    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/[email protected]
    
    Cc: [email protected]
    Fixes: 60f1d5e3bac44 ("ftrace: Support full glob matching")
    Reviewed-by: Masami Hiramatsu <[email protected]>
    Reported-by: Al Viro <[email protected]>
    Suggsted-by: Al Viro <[email protected]>
    Signed-off-by: Steven Rostedt (VMware) <[email protected]>
---
 kernel/trace/trace_events_filter.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 61e7f0678d33..a764aec3c9a1 100644
--- 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;
 }
--
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